>>1 back when I was in middle school I had a friend like that, I know how you feel, what happened to me seems like pretty much the same thing so I won't retell it. But what I can tell you is that she is no friend, she's two-faced and probably only cares about herself. What you need to do is to tell her that you can't be her friend anymore or just keep giving her the cold shoulder. She'll be pissed though and probably be immature and mean about it but it's really worth it... It's hard but being alone is better than dealing with that two-faced nature, it's way too stressful and quite the unhealthy relationship and you deserve better.
I went to a small school so for awhile I didn't have any friends at all but I always made sure that I was nice, and by being nice I made a friend and she's still my best friend to this day, she got me into anime and we're both nerdy. What I'm trying to say is that one day a real, true friend that you deserve will come along, for now tough it out and just ignore her as best as you can. You're a good person, a fantastic person, you deserve better and we Dollars are here for you :3