The angry little girl in The Piano has come of age. Now Anna Paquin is starring in X-Men, America's big summer blockbuster, as a cartoon vamp with a kiss that kills

When the 11-year-old New Zealand actress Anna Paquin accepted her Oscar from Gene Hackman and turned to at the audience, dumbstruck and terrified, it was tempting to think she had a dreadful life in store. It was 1994. Surely, her life would now spiral out of control. Chaos beckoned. Paquin, the second-youngest Academy Award winner in history, would be mobbed, first by reporters, and then by agents, directors and drug dealers. There would be cigarettes and booze, ill-advised relationships, rehab. Perhaps she would be like Drew Barrymore and fight her way back. On the other hand, perhaps she'd be like Tatum O'Neal, the youngest-ever Oscar winner, and quietly fizzle out. Where is Tatum now?

But Paquin has, apparently, not spiralled or fizzled. Here she is, in the Essex House Hotel on Central Park South, Manhattan, picking her way through a plateful of chicken and salad. The angry little girl from The Piano! And she's 18! She eats slowly, but not neurotically slowly. She is 5ft 5in tall now, and wears a tight, black formal dress. She is better looking than you thought she'd get. She has a good modern-actress look - her face snaps easily into a sort of darkly sulky expression. There is something of Juliette Lewis about her. She has grown up to be sexy, but not bland-sexy. Paquin's oddball-sexy.

She's not bothered about being 18, she says, shrugging. She shrugs a lot. 'At 18,' she tells me, 'you can get married, you can smoke, and you can join the army. But I don't want to join the army.' Does she smoke? Does she drink? She shakes her head so that her hair swings in front of her face. This, along with the shrugging and a sort of lip-chewing, is another of her gestures. You see it in her adolescent-period films, A Walk on the Moon and She's All That. Actually, that's how she still looks, 15 or 16, a touch younger than her age. She gives the impression of being a bit intense and unusual. Having chopped most of her hair off a couple of years ago, she's grown it long again.

Paquin is here to talk about her part in X-Men, her first role in a major blockbuster. Based on the comic books, X-Men has been directed by Bryan Singer, who did The Usual Suspects. Paquin plays Rogue, a dark, sultry girl who is not quite innocent - her usual role, in fact, and one she does well, because it's her. She has been known to say that she doesn't think much about acting - she just does it. X-Men , which cost $75m to make, has just opened in America, to mixed reviews and terrific box office, making $54.5m in its first weekend, and taking over from Men in Black as Hollywood's biggest-ever July opening. It's also the biggest-opening non-sequel ever.

The world of the X-Men is divided between humans, who are normal, and Mutants, who have special powers, but also disabilities. The Mutants, including a wheel chair-bound Patrick Stewart, and Sir Ian McKellen, represent minorities in general - they are blacks or people with disabilities. It's a clever idea. When Paquin's character touches or kisses anybody, she practically kills them; you see the life force visibly draining out. She says she read 'hundreds' of comic books to prepare for the part of Rogue. 'She's the ultimate adolescent,' says Paquin, who is sharp with literary metaphors. 'Frightened of being really close to others. Not knowing who you can trust.' Adolescence? 'It's hard to be detached from something you're still slightly living in,' says Paquin. 'You're in the process of becoming an adult, and you're changing - like, every few weeks you feel like a different person, and your looks are changing, and the way you see the world, and the way you see your family. Just because I do what I do doesn't mean I escaped adolescence, all the bumps and bruises that go along with it.'

So, as you can see by now, Paquin has not travelled the self-destructive route, nor has her career fizzled out. For seven years, she has attempted to do the impossible, to grow up normally and be a film star at the same time, and, if she hasn't quite succeeded, she's come pretty close. Eating her chicken and salad, poking it around a bit, but not neurotically, she talks about normal things: answering-machine messages, coffee, hanging out, and the importance of sleeping in. She likes sleeping in and sitting in coffee bars; she used to like novelty phone messages, and now dislikes them. She absolutely does not have any exercise or dietary regime.

Every so often, she will talk about something which is not so normal, such as being recognised by members of the public. 'Maybe you're in a public restroom or something,' she says, 'and you have, like, just woken up, or you're, like, at the supermarket or something, and you're just feeling, Oh my God - is this going to be their impression of me?'

Like Jodie Foster, Claire Danes and Natalie Portman, and unlike Drew Barrymore, Tatum O'Neal, Judy Garland and Shirley Temple, Paquin is going to college - this autumn, to Columbia in New York, where she will study arts and social-science subjects, possibly majoring in psychology. She is academic, despite having suffered a mixed, topsy-turvy education in an all-girls' school in Wellington, New Zealand; on the set of several movies, which she found a trial, and, for two years, in a Los Angeles high school. 'I have done pretty well in math,' she says, 'and I've always been pretty good at science, but English and languages and history have always been very easy for me.' She wants to go to college partly to gain experience of normal life - life outside acting. She pauses and says, 'For all the other thousands and thousands of kids that are going off to college this year, no one makes a big deal about it, and I'd rather be like everyone else.'

Paquin stopped being like everyone else at the age of nine, when she turned up, along with thousands of other girls, to audition for the part of Flora, Holly Hunter's screen daughter in Jane Campion's film The Piano. She does not, she tells me, remember much about her life before The Piano, 'just random things'. Her mother, Mary, is an English teacher from Wellington; her father, Brian, is a physical-education instructor from Canada. Paquin was born in Winnipeg. She has a sister, Katya, and a brother, Andrew, two and five years older respectively, both academic achievers; Andrew has since studied at Harvard and Katya debated for New Zealand at the World School Debating championships. Little Anna was, she tells me, 'the one that no one particularly noticed. She wanted to tag along, but couldn't.'

At nine, she hadn't acted before, unless you count her part as a skunk in a play at her primary school in Lower Hutt, a suburb of Wellington. 'I leaped on stage, and then skipped off,' she says. Her audition for Campion, a couple of years later, was startling. Campion describes her as 'this tiny little girl, probably the smallest of all I'd seen, and extremely shy'. In the audition, Paquin delivered the speech about how her mother had lost her voice, the emotional speech of a disturbed child. She was, says Campion, 'impassioned. You totally believed her.' What she had, said co-star Holly Hunter, was 'glorious instincts'.

Paquin tells me that, during the filming of The Piano, she 'wasn't really conscious of what she was doing'. She had a voice coach, who taught her an Aberdeen accent, which she pulled off pretty well. She scowled and raged beautifully. There seemed to be a dark monster inside this little creature. Her subsequent characters, as critics have pointed out, all seem to be a version of this one. What Paquin discovered at the age of nine is that she liked pretending to be somebody else in this intense way. She threw herself into it. It was not quite a job. She had no difficulty whatsoever. 'I was,' she says, 'so young when I made The Piano that I really didn't know that I should be nervous.'

The nerves came later, at the Dorothy Chandler Pavilion, when Paquin stepped up to accept her Oscar from Gene Hackman. This was when she first had an inkling of the hugeness of what she'd done. It was, she tells me, 'really scary. I remember being very very worried I wasn't going to be able to say anything.' She stood, in the words of one observer, 'wide-eyed and gulping for breath at the microphone for a full 20-some odd seconds'. Then she made a little speech and rushed back to her seat, rather than taking the more usual winners' route backstage. Hackman tried to call her back. Later, she told reporters that winning the Oscar was 'pretty cool', and reportedly fell asleep several times at the party afterwards.

And then she went back to New Zealand and attempted to get back to normality. After the Academy Awards ceremony, she went on a school camping trip. She didn't appear in a film for two years, although she flew to Hollywood a few times for auditions. At 14, she told a reporter she thought the Hollywood scene was 'kinda weird'. She did not display the Oscar. She kept it in a drawer. She was slightly haunted by it. In 1996, she played the lead in Zeffirelli's Jane Eyre , which was filmed in England; the director thought she was perfect for his dour, slightly cantankerous Jane. Paquin was sombre and reined-in; you could tell she was going to be good.

It was while she was in Canada filming Fly Away Home, a film about a teenage girl and her relationship with a flock of geese, that her parents split up. This, she tells me, was the unhappiest moment of her life. During filming, she appeared on set with a fake nose-ring - she'd found it in a 'neat junky jewellery store' in Toronto, and thought she'd shock the cast. But the director, Carroll Ballard, liked the nose-ring. Anna's character, Amy, wears it in the film.

When she was 15, Paquin moved to Hollywood with her mother, at first temporarily, to pursue her career. She told a magazine: 'It isn't likely that I'll have a boyfriend in the near future. Boys make quite good friends - it's difficult to imagine doing something serious with them, such as dating.' This was just before she played Alison in A Walk on the Moon, a girl having her first period in 1969 - during Woodstock, no less. Entering puberty, she played girls entering puberty; her most intimate teenage moments have been acted out in public. If you want to know how she felt about her parents splitting up, watch her as Alison, whose parents' marriage is also on the rocks. You can see a stormy mixture of rage and grief in Alison's face. When she talks to her father, played by Liev Schreiber, about the possibility that he might leave her mother (Diane Lane), it's moving; it feels genuine. In the film, the parents get back together; in real life, they did not.

By the time she was 16, things had changed. A Los Angeles high-school student, she had a boyfriend, and said, 'Sixteen is such a good age. It's so much older than 15. It's, like, 50 years older than 15. Fifteen is a nothing age. There's nothing you can do when you're 15 that you can't do when you're 14.' The Oscar remained hidden. 'I keep it at the back of my closet, with my shoes,' she said. 'I don't want to look at it every day. I don't want people to come into my room and think they have to talk about it.'

It hasn't always been easy at school. She left friends behind in New Zealand, and made new friends at high school in Los Angeles. But she misses the old ones. Her accent is now more than half American, with the Kiwi creeping through. She'll end up sounding almost American, like Mel Gibson. She says, 'You're definitely shaped by the culture you've been brought up in, and even though I couldn't tell you exactly what it means to be a New Zealander, I think I've been influenced a lot by that culture.'

She lolls her head and thinks for a moment. She says, 'I don't know. I mean, I love the people I've gone to school with, but sometimes I'll just really want to talk to someone back at home. And I don't know exactly what triggers that off. I'll just suddenly be, like... there's something a little bit different. I don't know.'

Paquin understands the importance of being 'good friends with people who I absolutely know are being my friends because they like Anna, and they get along with Anna, and they want to be my friend, and we connect as people. That has nothing to do with the fact that I have a career. I've met people that I know don't like me, they're just a little bit impressed with what I do, and I guess that's understandable. Usually they get bored because I'm really not that interesting. But, you see, I kind of like that. Maybe they think I'm something special now, but give it a week and I promise you they'll be toddling off back to where they came from. I'm very ordinary. I don't feel like I do anything.

'I haven't entirely figured myself out,' she continues. 'I've got a long way to go before I figure out something as deep as that.' She likes the MTV cartoon Daria, about a teenage girl with a dark, cynical take on the world. Her favourite actress is Holly Hunter. Her favourite TV show is Sex and the City. I ask her if she thinks the female characters in Sex and the City are supposed to be victims.

'I've no idea.'

Doh! Of course she has no idea - she's a teenager. When you talk to her about her ambitions for the future, about what she might be doing later in life, she wonders what you mean by the future. For Paquin, the future is next week, or next term. I ask her what she'd like to be doing at 40 - the age when many really good actresses begin to think they might win an Oscar. Paquin says, 'Forty?' It's a concept at the edge of her understanding. It's light years away. 'I don't know,' she says. 'I probably hope that I have a family, and if I still want to be acting that I'm acting, and if I want to do something else that I'm doing that.'

One thing she likes to talk about is photography. 'Something I like to do,' she tells me, 'is sit somewhere on a crowded street when no one can really see, out of the way, and then take photographs of people just candidly as they're walking past when they don't know you're there, and it sounds kinda like you're a stalker, but honestly I'm not. Sometimes it's more interesting to photograph somebody when they're just being themselves, because they're not projecting an image of how they want to be seen. You get to see who they really are.'

Paquin likes photographing couples. 'It's interesting photographing them and then playing "guess what was going on right then". Deciding what the dynamic was, whether they are happy, what they are truly feeling. It's a little bit of a game, and it's all just sort of fictional, but it was fun to decide what was going through that person's head, you know, if you see someone before they've pasted on a smile. Sometimes you can see something in people which you wouldn't otherwise get to see.

'I don't think there's any character I couldn't be,' says Paquin. It seemed highly unlikely, but it looks as if she's just about made the transition from child star to adult actress. Who knows - she might have quite some career ahead of her. In the meantime, she says, she wants to do 'not a whole lot. It's summer. I've just left high school.' She wants to mess around like a normal teenager. Like, she tells me, she recently took some self-portraits, using a bendable mirror. She loved the results. 'You get this crazy-looking distorted image,' she says. She laughs. 'Four eyes and two heads. Like, an alien-shaped body.'