Lina is a sorceress in training. She travels around the world, seeking out new spells to add to her list. Along the way, she takes on various odd jobs and destroys bandit gangs in order to get money. And she needs it, what with her and Gourry's enormous appetite.
Lina is quite petite for her age. Gourry is forever making comments about how flat her chest is, in fact, he thought she was a kid when they first met. That usually earns him a hit on the head, or a Fireball.
Lina is usually hot tempered, especially about her size. She does have a weakness for food, in fact she can out eat Gourry--who is much taller than her. Strangely, she never seems to gain weight. I believe the excuse that magic may make you use up a lot of energy, thus eat more, since traveling alone wouldn't let her out eat someone like Gourry.
Even with all of her power and attitude, Lina isn't without fears. Slugs nearly top the list, right behind her older sister. You see, Luna is the Knight of the Dragon God Cephied, and has powers Lina could only dream of. When they were young and times were tough, Lina took pictures of Luna taking a bath and sold them for cash. Ever since then, Lina has listened to Luna's every word, in fear of what she might do.
When she first travels (the OAVs), Lina's companion is Naga, a sorceress with towering proportions. They go around on several adventures over a two year span, before Naga mysteriously disappears. In Episode 1, Lina is fighting a bandit gang, when Gourry comes to help her--thinking she's a damsel in distress. He turns out to have the legendary Sword of Light in his possession, and so Lina follows him in order to get the sword. Along their journey, they meet up with Zelgadis--a young man cursed to be in the body that is 1/3 human, golem, and demon; and Amelia--the princess of Seyruun. Together, the four of them fight of demons and monsters that attack their world.
Lina has had other companions as well. There's Sylphiel--a shrine maiden who is in love with Gourry; Xellos--the general/priest of the Mazoku Lord Zellas Metallium, who can be enemy or ally, mattering what he is feeling like at the moment; and Filia--a Gold Dragon priestess for the Fire Dragon King. Also, she's forced to put up with her "rival", Martina--a princess who's country Lina destroyed on accident; and the bounty hunter Zangulus--who wants to defeat Gourry in battle; who eventually get married in the final episode of Slayers NEXT (and the church's front wall falls on them too). They do help Lina out at times, but are really only there to show up their rivals.
Lina has the command of the strongest spells in the whole world. She is the only living sorceress who has summoned the power of the Lord of Nightmares--the strongest Mazoku of all. Lina sealed away the Giga Slave, since she could accidentally destroy the world through it, but still has the other spell, Ragna Blade. With all this power to burn, it makes little sense for her to need to command the power of Gourry's Sword of Light. I--along with most Gourry/Lina shippers--believe it is just her excuse to not tell him why she really wants to travel with him. Especially since he loses it twice: first after Slayers NEXT, when he uses it to help him reach the Lord of Nightmares to get Lina back (she was willing to go and help him find a new sword, then Xellos returned the Sword of Light to Gourry and Lina got mad), and the second time is when he gives it back to its creators after Slayers TRY. And they're still traveling together, aren't they? They're shown walking away from the viewer together in the final clip of the series.
Many episodes of Slayers feature Lina in a restaurant at one point, and woe to the owner. The first episode has her order half the menu.
Favorite spells: Fireball, Flare Arrow, Dragon Slave.
Even when the chips are down, she can still pull one out of her *Ahem*, due to a well shot Dragon Slave/Ragna Blade/Giga Slave.
No matter how weak she is, Lina can always go anywhere for food.