I suspect most of the advice here will be to the effect of 'she cheated - the relationship is over and you should move on'. A valid argument, but I would like to present the other side. You are 22 and she is 24. You have been in a relationship for 7 years, i.e. since you were 15 and she was 17. Statistically, I assume that this has been the first relationship for both of you. Being with someone for so long from such a young age... it is not uncommon at all to feel one has 'missed out' in a way. Sexual and relationship exploration is part of growing up - even if one has a stable partner throughout puberty (which is quite rare), the urges remain. I would suspect that is something she might be going through and, with the vulnerable state she was in, she caved in to the temptation. But if that is so, I don't agree that this was a standard 'she is a bitch, she cheated' scenario. My parents have been in a similar situation to yours and the very same thing happened in their 20s. They sorted it out and have remained together ever since (closing in on some 40 years now). They're not the only couple I know of to have gone through something like this. Some fail, true, but some deal with the causes and can make it work. It could well be that this is the first step towards the end of your relationship. It could also be that she is just confused and, seeing as she has skipped a chunk of development by being in one relationship since she was a teen, she now does not know what to do. My advice would be to sit down, the two of you, and have a good chat about what happened, why it happened and whether there are any doubts or feelings she isn't telling you about. You know her best - from that, I hope you will be able to judge whether to move on or whether to work through it.

This is the advice after the guy's girlfriend of 7 years got shithoused and let some random guy from a bar 'convince' her to cheat. The fact that someone would defend her actions is rage inducing. At least all of the other advice was realistic I.e. ditch the slut.