This is interesting. Without knowing all the details I would avoid her like the fucking plague.

I have wasted hours trying to get with girls who are with boyfriends "who are twats". They will flirt outrageously with you, but they will never leave there prick of a boyfriend. They fucking love that emotional rollercoaster shit.

Anyway.

Did you make your intentions clear from the start? Most woman have to be told numerous times that you just want to fuck them. If you did, and she is still treating you like a stranger then forget it. Move on.