Please I need help what do I do?

So I have 2 best friends. Then this new girl came and she was really annoying and no one liked her and she kind of started hanging out with us. Recently she has really latched on to "amelia" and for a while amelia sounded really annoyed. She would complain to me about it. But for the past month, amelia and this new girl have been hanging out every weekend and going places, while me and "lucy" are not invited. They go to movies and restaurants and sleepovers. Amelia and this guy are starting to have a thing, and she wouldn't even confide in me and lucy. She only talks about it with the new girl, and they even planned this whole double date thing without us. At lunch they sit and talk about their plans and what they will do next weekend right in front of us, and we aren't invited. The worst part is the new girl will come and brag to us about what she did. Amelia has been acting really differently and exclusive lately. She totally ignored me and lucy. And then this week I got this bad and grade and on top of everything else I just lost it. Lucy was comforting me but amelia said to another friend "summer" - "I don't see why she is making such a big deal about one test." How could she say this? She has been my best friend for years. this morning Summer and Lucy talked to Amelia about how she has been acting, and Lucy told me she apologized and seemed generally sorry. But Amelia never said anything to me. I really just want to talk to her about everything but I don't want to start a big fight. How can I just make things go back to the way they were?