Ladies, particularly young ladies. What is so attractive about jerks?

I'm 23, and I've kind of been having a thing going on with a girl my age. But, I can tell that she likes this other guy, that she has even admitted is a jerk. Is it immaturity? Does she still have the same mind of a high-school girl? That's the only thing I can come up with. Also, is it just exciting to be with some guy whom is amoral? Thanks.