In 'House of 1000 Corpses', we have the one 'Alice in Wonderland' girl who survives? throughout the movie, while every other member of her original group of friends has been killed off. She has faced down all the masculine killers, and has successfully persevered through the trials.
This is similar to the views of Brownmiller, Dworkin, and Solanas (society for the cutting up of men ;), where the victims must stand and stop being victims. I think the David vs. Goliath feature of these movies only reinforces the idea of the strong female character. But, this struggle of victim versus oppressor never ceases, there is always a sequel.
The huge dividing line is the societal sexual baggage that goes along with our notions of innocence and purity, i.e. vestal virgins. Which is also what helps Brownmiller and Dworkin's arguments that men just destroy, in that men are the despoilers of the pure. The female accomplices tempt us with sexual fruit, daring us into the land of original sin, guilt, and punishment. The male killers have sex on them as well with their superhuman strength, big "knives", and very sexy non-communicative behavior. ;)
I don't think either sex gets a fair shake in horror films, but we do see some surprisingly strong female roles (Laurie in Halloween, Nancy in Elm ST, Alice in Friday the 13th).
Another interesting thing in 'House of a 1000 Corpses' is that it, like 'American Psycho' is a satire which has us viewers walking on the "wrong" side. When Piggy gets killed in 'Lord of the Flies', we're supposed to feel bad. In both of these movies, we're not supposed to care, we are supposed to want the rabbits to run, to want to have the chainsaw hit the girl. I think each movie does its job in this regard. If we fell into the film, then have to ask ourselves why? How is it that our morals are swayed by a story line and some music?