Student Exchange Programs

So my girlfriend and i have been going out for 2 months. we have broken up once already but we got back together shortly. 2 days ago she was telling me about this exchange student who liked her. He hits on her all the time and he makes sexual suggestions to her all the time. This kid has a reputation for getting in girls pants and doing everything he can to get there. Earlier this year he got in alot of trouble because he tried to rape a girl.

Yesterday, she told me she was hanging out with him. She didnt text me back for 4 hours and then she said sorry i was busy… and i said what does that mean. She replied Excuse me? And i asked her if they had done anything. She got really really mad. we got in a huge fight. I told her that i trusted her but not the guy and that i know she wouldnt do anything like that but he will stop at nothing to get it. She broke up with me but we are still fighting and she said she wants to give me another chance to but is afraid.

Is this a good reason for her to break up with me? and is it a good sign that she still is fighting with me? I really really like this girl and she knows it. I just dont understand what was wrong with worrying about her.