J.M.
I had a similar problem with my son in 6th grade. Some bullies at school tormented him and anyone who was friends with him. It was a new school for him so he ended up with no friends and was beginning to get very depressed in general, going and returning in tears every day.
Talking to the teacher is a start, but if that is not getting you anywhere, perhaps it needs to be elevated to the Principal of the school. I would suggest talking to the teacher again and letting her know your feelings and that things need to change or you will have to speak to the principal and/or put your daughter in a new class. This was hard for me to do as I did not want to upset the teacher either, but we have to do what is needed for the best interest of our children. Of course it should be done as respectfully as possible, but be firm and perhaps have some suggestions as to what specificially she can do to help the situation.
Unfortunately for my son, the principal was not able to help him. The kids at the school were too far out of hand and the parents were unresponsive and uncaring. I decided to go ahead and homeschool my two children now in 7th and 6th grades(actually a virtual school they work on from home with my help & supervision). My son is much happier now and has many friends at his new school who he meets with on field trips, etc. He has also formed some good friendships through church, boy scouts, and sports teams he is involved in and is bouncing back quite nicely. I hope the same for your daughter.