Tell her to stop and tell a teacher. If it happens again then hit her right in the mouth.

Might sound harsh but my father told me to do the exact same thing when I was her age and I did, bloodied his nose pretty bad. Yea I had my parents called but my dad told the teacher that hadn't done anything abt it and it continued so I had to take care of it.

Or you could tell her to do what my brother did which was throw a kid across a classroom table after the teachers did nothing for months. And this was at a private school and the bullies father was a member of the board. Kid never messed with my brother again.

So there you go, one "violent" way and another more defensive type of reaction.

If these kids arent goin to be set straight at an early age then it will only get worse.