What do you do when you know she's into you but she shouldn't be?

So there's a solid HB9 in my Eng. class... and she KNOWS IT. We're about half way through the semester which I spent pretty much establishing myself as alpha in the class. Worked like a charm; the whole class loves me and the girls always try and talk to me.

I laid this ground work mainly for this HB9 with the occasional neg, which has won out. We spent the whole class yesterday flirting like crazy and I kept catching her watching me when I wasn't paying attention.

We left class where I just didn't seize an opportunity to get her number which was dumb, but we talked on Facebook that night. We joked a little and she ended up abruptly leaving me in the conversation.

The only issue is that she has a bf (classic large, macho kind of guy) and I feel like she is controlling herself when she talks to me. Maybe gets in and then winds it back because she realizes her bf. Or she could just be hot sh1t and knows it.

Any chance I'm right, and if so, what can I do about it?