Very Confused on what to do, please help?

I had a friend that i considered to be my best friend. But things changed when she got a boyfriend and she forgot about me, changed her attitude and wasn't very much of a friend anymore. To the very end of our friendship i became friends with my very current good friend. We weren't as close as we were now. So basically we became a trio. But the whole issue with my former bff was that we always argued practically daily, she started to irritate me with her changed personality and we broke things off after the last blow we had. This whole thing was a year ago. She isnt very liked at school at all. We hated each other for some time but i got over it and moved on. Now she has conflict with my current good friend and is trying to get me back. She feels like I was stolen from her and that she was wrong about treating me badly in the past. She is trying very hard to get things back like they were, and im not sure i want that, she noes that i kinda dont, but she still pushes hard. WAT DO I DO?