Can I win her back?

I be had a weird relationship with this girl. At one point she said I'm nicer then all other dudes and make time for her. Anyways she asked me about dating two months ago and now she is back with her bf.... I swear when ever she has guy trouble she come right back to me. However... That's not the case this time. I told her how I felt and she basically deleted all contact information from me. She said we could be the best ever and now this happens.

She thinks I screwed up our whole relationship. It's not my fault, I was trying to figure out if we were friends or more. Just like when she asked me. .... Anyways how do I win her back? Steal her from her bf and **** her like we should have years ago?ive invested too much time to be this close to the finish line. It's unfair how she teased me over the years and not giving out. All I want is to bang, just to see what it would have been like