Where are your friends? Ask them to stand up for you. Does she bully anyone else? A bully preys on the weak (and remember, a bully is someone with their own emotional problems), but if you can out number her then she’ll be intimidated.
Otherwise, if all else fails, tell someone at your school, like a teacher you trust, the school nurse or counselor or the principal. If you feel that she won’t be punished on lack of evidence, use your phone (I’m sure it’s a smart phone) to record the encounter, use a voice recording app and hold it at your side.