Look man, this isn't even an advice thing that we can give you. There is only one person who knows whether you should stay or go, and that's you.
You have to look at some things for yourself. You're going to have to evaluate whether the emotional investment you have in her is or is not more valuable than the trust that you have lost here. You have to ask yourself if you think this was a one time mistake, and that now that she sees what she's capable of when drunk, if she'll avoid a similar situation. You have to ask yourself if you're going to be able to forgive her and let it go, because these are the nasty things that, if you don't let them go, will ultimately destroy your relationship anyways.
This one is up to you, no one here can answer those questions for you.
EDIT: Actually, I feel like elaborating a little here, because every time I see a topic like this, I think the same things. So let me tell you why no one here can help you. First off, the truth is that we don't know you, we don't know your girlfriend, and we don't know the ins and outs of your relationship. We don't know her well enough to know if she really will try harder next time, or if she'll be pissed off that you weren't more mad at her for cheating on you. We don't know you well enough to know if you're the sort of person who really could forgive her for this, or if you're the sort of person who would keep bringing it up and ultimately destroy the relationship anyways. We, really don't know anything, except for the details you have shared with us. Details which, I would guess, probably don't really capture all the facts, and because the lives we all live are so complex, you probably never could give us all the facts. Anonymous people simply aren't familiar enough with your situation to give you good advice.
But there's a reason that people always come here, time and again for anonymous advice. It's because getting anonymous advice allows you to let someone else make your decision for you. Life is tough. For every single one of us. It's full of good and bad, and sometimes it's great, and sometimes it sucks shit. And one of the worst parts of life, is owning up to our own decisions when we make the wrong call. That is why time and time again we look to other people to make our decisions, because that way we don't have all of the responsibility anymore. You can take the easy way out, and listen to the other people here who, just like me, really don't know enough to give you a good answer. Or, you can take the opportunity to look deep inside yourself, and make a decision that you will be completely responsible for, even if that is a hard thing to do.
