Oh dear this sounds like my childhood. I suffered for years. I found my confidence eventually. Karma will prevail. I wish I could advise but I dont think u can do anything. Just keep an eye on her and tell her things can only get better, and they will. I wish I stood up for myself but it wasn't in my nature then. She will be ok and more than likely do far better than these so called friends will.
Sounds horrible but my daughter has been enduring" evils" as she calls it, being left out, being told she will be left out because ..............dont like her, girls getting up and moving and saying I don't want to sit next to .... I hate her, being told she has to walk a different way home because .....are walking this way, she went to a party tonight it was suppose to be 5 til10 but came home at 7 as the girls said oh she is here and then said she was the reason the other girls wouldn't go then gave her "evils" the rest of the time, I don't know what to do these are her so called friends! She says she cries at night because of it and when they are horrible at school she finds somewhere quiet to sit and cry, she is 14 but not confident enough to tell them where to go, the school are being supportive but they can't be there all the time, I feel useless ! It has been going on in waves for years!