I though their dynamic was a really interesting one, I just could never buy Stiles as that character. A sweet, wholesome girl like that gets raped and severely brutalized... and then decides she's going to become a serial killer and hunt down her attackers? Yeah right.
Maybe if she had already been a fairly dark, troubled character (like a Lisbeth Salander type), and this is what finally sent her over the edge, that would make sense. But not the way they presented it.