True... I am making an assumption. I wasn't there to observe your relationship. I've never talked to this girl, I have no idea what she is like. But I have a hard time believing that cheating is out of character for her. Therefore, I have to assume that there were plenty of situations beforehand that should have warned you of what to come. The way you phrased your response - "more than half of the time if she did something like the stuff you listed i would speak up" - makes me think that you actually know what I'm talking about, but are not willing to take response-ability for it. Btw, "an average argument a couple might get in to" is not agreeing which movie they should go see tonight. The examples I gave (obviously based on my own standards) are not an argument. In my life, anyone who lies, disrespects my time, breaks promises, or is rude to my friends gets a warning (meaning I explain why I will not tolerate that kind of behavior) and then is summarily dismissed if it happens again. It's not a discussion. Accept that it is not your job to tell other people how to behave. But you have to tell then how you expect to be treated and never compromise. You have to get out of the victim mentality. The more you think that "She did this to me" or that "How could I have known" the more you give up control of your life. Understand that neither of you are at fault. Accept the fact that you weren't mistreated and you didn't mistreat her. Both of you did the best that you knew how. The same with her roommate. Although you might regret your actions, at the time you didn't know there was a better way. Think through that situation. Let go of guilt. Accept that you have learned the lesson and will not do that again. Then I would highly recommend that you go and talk to the roommate. Tell her that your actions were wrong, that you had no intention of hurting her, and that you now know better. You never know, you might actually make a new friend (or more.) If nothing else I guarantee you'll at least gain a lot of respect in her eyes. And remember, girls talk to other girls.