Should I go for a girl who I'm not sure I have feelings for beyond physical attraction?

There is a girl in my class who I have liked for around three years. We are both freshman and she is currently dating a junior. Other people in my class don't like her that much, for example she has done some slutty things that piss people off. Anyway, I like her more of as a girl not so much a person. I don't disrespect her, but I still feel like she isn't someone who I would want to date for her personality. At a class party recently she was flirting with me even though she is dating. She even brought up the idea of her breaking up with her boyfriend and maybe seeing me. I'm not sure how I feel about her doing that, as well as the fact that I don't think I would want to date her when it comes down to it, just fool around maybe. Should I tell her I like her?