My oldest didn't suffer unduly at school, but was beat up for a time, unbeknownst to me, by his younger brother. When I found out, he told me he did not defend himself because he knew he would get in trouble. I told him I had never and would never hurt him the way his brother had and he needed to defend himself even if he was grounded for it, that not defending himself was worse than anything I would ever do to him.

Teach your daughter she does not need your approval. Teach her to make her own decisions, even if sometimes other people don't like it. Help her figure out how to make good judgement calls in the face of difficult circumstances. Give her opportunities to make real choices and back them even if you do not like them. Let her know you don't like all of her choices but you accept them and respect her right to make them. Do not make her dependent on being liked and approved for everything she does.