So a friend of my girlfriend keeps hitting on her. He is very persistent and even tried holding her hand the other day. She has told him numerous times to stop and she only loves me like that. He doesn't really listen and keeps trying. She doesn't wanna lose her friendship with him but I think she needs to be more assertive and tell him if he doesn't stop their friendship is over. I don't personally know the guy myself so I can't even talk to him. What should I do?