I would also be having a talk with her parents. Does she bite at home? Does she have siblings? How do they deal with this behaviour? If they aren't on the same page as you, then it will be difficult to curb the behaviour. I agree with the loss of priviliges. She is old enough to know that she is doing something wrong. I would also maybe set up a time line for her to curb this behaviour and let the parents know you mean business, as you can't allow her to be hurting the other children in care.