Is this a good reason to break up? ?

ok so this is kinda long.this halloween my girlfriend and i went to some party. as all girls do she wore some sluty costume, thats w/e. So i'm standing in a parking lot with her and some guys pull up all drunk in a car and say "oh man look at that a-s-s and t-i-t-s!" so i stare at them and i was about to walk to them and say something (they were highschool punks) when one of them says hi to my gf, and she says high back all flirty! then she says "i didn't hear them say that" not only that but later on that night she is being bother by this drunk guy that is trying to hugh her its one of her friends! so i was gonna push him but she told me to stop b/c they were friends. then i tell her the next day that i 'm gonna scare him by going to his shcool and you know.....and she says; "you do that and its over, don't lay a finger on him he is my friend" so i'm like pretty sure that this is one of those things where its over. but sometimes she says i'm crazy. what do you think???