Friends? or Not Friends?

One of my best friends has dumped me and gone of with her best friends yet I am friends with all of them and it makes it hard to talk and joke with them cause shes always there. I did nothing at all to her yet she makes my life a living hell because she wont let me apologize and I don't know what I did to deserve this.
I am still friends with the other 2 yet something has changed because me and Keely ain't friends Emily and Chloe seem different. Shes just acting childish yet I have know her for 2 years nearly 3 and she has never acted this way before. I don't know what to do because if Emily and Chloe leave me I'll have no one like last year and I don't think I can go through that again. I have spent so much time trying to figure this out yet I don't know whats wrong. Its killing me inside because at one point we was awesome friends yet now we have drifted apart and I know that happens to the best of friends yet I have done nothing wrong...
I just really need to find out whats wrong.

What could be wrong?
I'm so lost right now I don't know what to do...
Elle
xoxo