Cute Goth Chick

Ok, so last semester in my art class I met this really hot/cute goth-like chick who on the surface seems really naughty and bad but when I got to know her turned out to be a nice good person (both of which I consider good things, naughty AND nice)... She obviously liked me, and when I asked her she admitted it. The catch is, she has a boyfriend. The catch to the catch is, she called me "just like" her boyfriend, "except better looking and less possessive" (possessive is a bad thing), and even invited me to bed with her and her boyfriend on the condition that he said OK (he didn't). But because she really is a good girl, she refuses to leave her boyfriend even though she admits I'm better than him. However, even though the boyfriend is jealous and possessive and doesn't want her hanging around anybody attractive, male or female (did I mention she's bi?), the girl and I still spend all the time we can hanging out together, with a very obvious attraction omnipresent... but never acting on it.

What do you think my chances are with her if things keep up like this?

If by "be a complete and utter doormat" you mean "do whatever she asks in some vain hope of getting laid", no worries. I'm superfluously nice to her for the same reason she is to me: because I enjoy getting positive attention of any sort from an attractice member of the opposite sex. It's not sex, but it's better than sulking in a corner by myself.