Unfortunately, it seems that the majority of kids these days have no respect for themselves or anyone else. The small group of kids that DOES have respect for themselves and others seems to be the group the endures the bullpoop.
My son has been suspended this year for punching a boy who consistently bullied him. The punch came when the bully came at him swinging a piece of wood in shop class. Unfortunately, my son didn't want to document earlier instances, so he was suspended along with the other boy. Not sure what's happened since, but my son tells me that the other boy is no longer in school.
I don't normally agree with Anne/Ducklite, but I think she has given you excellent advice. The MySpace idea is also great.
I hope your daughter is okay and will not have to deal with this in the future.
I thought you said "girls" in your OP, but followup posts just mention "the girl" -- what happened to the other one?