My brothers girlfriend is really mean to me and it is upsetting my brother. What should we do?

My brother is 2 years younger than me. He is my only sibling and we get along really well and are really close. He dated this one girl for years and they broke up and his heart was broken. Then he met this new girl who everybody raved about and she seemed really nice and I thought she and I had a lot in common. But then all of a sudden she started being mean to me and picking on me in front of all these people. She embarrassed me and said that my boyfriend was gay because he was from new york. And she constantly laughs at me. My brother is in serious denial about it he can't afford to have his heart broken twice. If there was a fight I would win hands down she is only 90lbs and frail and I am a soccer player and athletic build. I feel like I just got to put her in her place. I have been ignoring her for my brothers sake. What should I do? I miss his old girlfriend but i'm not sure if it would be healthy for him to go back to her. Help!?