First of all, tell your D to speak out for herself, look directly to that girl's eyes, says:" Stop talking to me like this, I don't like it." firmly for a couple times, hopefully, it will scare the girl away.
Tell your D that you are always on her side, "if the girl still bothers you, tell Mummy, Mummy will talk to the teacher and the girl's parents to help you resolve the problem."
Don't tell your D to just ignore the girl, most of time, kids need to be told what is right, what is wrong.