How involved is the school?
My DD was bullied at school. On the advise of her counselor, we switched schools mid term b/c she was self harming and her life was horrible. The switch was a great thing for her, she did really well, and because it was an odd time of the year to switch, she got some extra looking after from the counselors/teachers.
I also agree, get her involved in some activity that involves children from other schools/places after school. And, make sure the school is taking action, and seek assistance from the counselor.
Hugs, many hugs to you and your DD!
I come from the camp of taking bullying very seriously.