Relationship Help Question

I have a question that i need some advice about. So here the situation my g/f has been texting this guy for a while that is her friend. She was interested in him during a brief period of time that her and I broke up for that lasted about a month. About 9 months later she went home from the weekend (we are away at college) she never called me or texted me (which she does non-stop) all night that she was with him downtown until about 5am on her way home. So we had an argument about it so anyway now this was about month ago and this weekend we got drunk and passed out and she texted a different guy that happen to be her ex boyfriend and it said "I want you". I need some opinions on this because i dont know what to do. Im sure she wouldnt cheat but it seems she is very interested in other guys. When I brought this up to her she obviously used the excuse that she was just drunk and made a mistake for texting him. We have been together for just about 3 years.

What does everyone think?