Problems

If you and your girlfriend were going out for awhile and a friend of hers and you got into a fight, not fists just words exchanged, and then a week later he comes to your house and he and her talk and it ends up making her cry so you and her don't talk to him anymore. Then months later she tells you she isn't that mad with him but just you are, do you think that she should back you up and stop talking with him and about him? Theirs this guy I know that I hate because of this situation but my girlfriend just told me she isn't as mad at him as I am so now I don't know what to do anymore, I'm confused to what I should do about this. . .