Ok. Think about this:
You didn't go to that party intending to make out with 7 guys. In fact, I'm guessing you were looking forward to hanging out with this guy .The reason that you did this was because you saw him making out with someone else, and you got jelous. And why do girls get jelous of other girls? In situations like the one you endured, it's because you really care about this guy so much that it hurts to see him with anyone else. Of course, your first reaction, like you said, was revenge. And of course revenge is not always the best option, but you were angry, and therefore probably not thinking straight (not to mention you were at a party). In retro-spect, what you did was wrong, and I'm sure now you even realise this. BUT, just so you know, a lot of people would have done the same thing. He may not see it, but it is some kind of symbolism. It shows you care enough to be hurt.