If, at some point, she's going to help the heroes, then you might go with "Survivor Girl". Basically, the heroine of a slasher flick who survives against all odds. At the start she's just a pretty girl, maybe a bit special, but she's driven to find something special in herself that will allow her to survive.
And yes, I'm borrowing the phrase from Behind the Mask: The Rise of Leslie Vernon - a movie about a journalism student doing a documentary on Leslie Vernon. Vernon is in training to become a serial killer and takes the camera crew behind the scenes as he prepares for his first murder spree. A dark yet funny movie.
Richard