BUFFY'S PROPHECY DREAM

Buffy has a disturbing dream which mixxes past/present/future?/in a tangled web.
Is Buffy's arrival in the 19th Century in response to a call for a new slayer, is she there by accident, or has she been there before.

Spike has fought two Slayers in the last century, and...he's killed them both.
Giles
The last Slayer I killed...she begged for her life.
You don't strike me as the begging kind.
Spike
You shouldn't have come here.
Buffy
I'll make it quick, it won't hurt a bit.
Spike
No Spike its gonna hurt a lot
Buffy

I can't see her. The Slayer. I can't see. Its dark where she is. Kill her. Kill her. Spike. Kill her for me.
Drusilla
I did a couple of slayers in my time. I don't like to brag. Who am I kidding I love to brag!
I'm going to leave this one for our friend here.
Spike