GF talking to her EX

So, im with a serious relationship with her for almost 8 months, but, before me, she had an 5 years relationship with another guy, and, still when they broke up, she whould still have pictures of both of them in the facebook, after we started dating, i had to convince her to delete those pictures with the guy, she said that still considered him as a friend, and i know that he still loves her and wants her back, i couldnt stand the fact that my gf was talking to a man that wanted her back, so i made her choose between he and me, she "chose" me, and i said that if i knew that she was talking with this guy again, i would brake up with her, so, TODAY we were in a bar, and i had her phone in my pocket, and i went to the bathroom (i know im wrong in this part) but i went for her facebook conversations and found out that she was talking with the son of a b***ch, the last chat that they had was YESTERDAY, they were not talking dirty thing or stuff like that (i didnt had the time to see everything), but he was calling her things like "my angel" and stuff like that, after i saw the conversation, i went back to the table and pretended that nothing hapenned, but i cant stand this kind of thing, so i dont know what to do, i REALLY love her, what should i do? talk to her? brake up with her? i cant remain in silence, this is killing me by the inside. (sorry for my english, im brazilian)