PROBLEM! My girlfriend pulled me aside to admit that she had sex with someone else last week

Well, not exactly okay. You care enough to whine about it, but not enough to actually impose any real consequences. And if there are no real consequences, I’d cheat on you, too. Who wouldn’t?

There are a lot of women in the world. You’d be dumb to settle for this one. Do you really, really want to stay with this cheater? Or are you just afraid you won’t find someone else easily?

Also note that this wasn’t just a sudden thing. Let’s put it this way-she had a boyfriend [you] for a full year. She got a text message or a call from a guy- which she could have ignored, said no, or come up with a fitting excuse. But, she thought about it and she then made a decision. She left. She knocked on his door. She went inside. She started touching him, kissing him, clothes started dropping off. She probably even gave him a BJ which he returned by making her call him dtadty. This wasn’t some impulsive thing. She made many, many deliberate decisions to cheat on you- and she did. Why go back?