What to do....What to do..PLEASE HELP.?

So here is the scoop im 22 and this girl is 21. I've known her for 6 years.We were dating for 2 months a month ago. she was in a relationship for 4 years and i was the man on the side for 2 months before we started dating. When we were dating she would keep contact with him and we stopped talking because she went back with him. When she was with him previously to them breaking up (right before we started to date) she was texting me all the time when she was with him. Now that she got back together with him she told him that we dated and had sex or whatever. So he told her to stop talking to me and seeing me etc. even deleting me off her facebook. She got into contact with me about 2 weeks ago. We have seen each other on the side but have not cheated. This is a screwy situation and hard to follow, i know. But recently, she has been putting statuses up ( my friend tells me her statuses) about how happy she is with her boyfriend and what not. Why do you think this is the case? I feel as though it really isn't because she is happy. Why wuold you need to brag if you truly were? Anyhow, i've gotten to the point of being absolutely pissed off. Pissed off because for 6 years of knowing her she always has chosen her exes and given them 2nd chances, i did not get a true solid shot ( when we dated, she was still in contact with her ex and wouldnt tell anyone we were dating) obviously she always wanted to get with her ex. What advice i need and could use, is how should i handle this situation? should i remain friends with her even though she is bragging about being with this guy and it hurts me? should i tell her off? should i ignore her? I feel truly and deeply hurt. I feel as though i am a sideshow option B until thigns come crashing down with her and her boyfriend. I really do not know what to do. I want to mature about it, i've known her for 6 years, but i just feel **** upon. I feel lead on and devasted. Please help.