lesbian girl getting yelled at in bathroom..

My girlfriend has short hair, and wears men clothes. But by no means looks/walks/talks/wants, to be a MAN 
Every time she goes into a public restroom she gets yelled at by women because they think she's a male. She simply tells them she's a woman and they still continue to bash her. 
Sometimes even bashing her infront of tons of people.. yelling.. cussing 
What would you do? She's too sweet to fight back. I feel like I'll rip someone's face off if they mess with her. 
Disclaimer: once again she is NOT trans