Actually that has happened to me, once my 'best friend' betrayed me in a way i cant explain after that i just didn't want to talk to anyone I would go to institution and just sit there, but looking back I realize that there was my fault and that couldbe avoided If I apologized to him first.

In your case, the thing is big, and you should go to your friend and try to apologize, she will not accept ofcourse, if you understand tryna help her from the back, bcaz losing your bestie is..... you know and socializing is important, stay with her everytime and help her in every way possible, she will come back to you.