Since she was awake for the first part of it and was a willing party until she fell asleep, I don't think it's something you should beat yourself up over. If she had been awake, she would have most likely continued until you guys were done anyway, so I wouldn't sweat it.
Now, what people are saying on the other hand is terrible and I can only imagine how you feel. It must be humiliating as all hell, but as long as she's not freaking out about it, I don't see it as being an issue.
People can be pretty damn cruel and blow everything out of proportion as you can see, so obviously it was a bad idea to tell anyone about it, but since you can't turn back time, all you can do is wait until the dust settles.
If your girlfriend left you in a heat of rage, then I doubt the dust would ever settle, but if she's seeing at as no big deal, people will eventually shut up. It may take a while, but eventually they'll get bored and find someone else to pick on.
Best wishes to you and your gal.