Finding it very difficult to forgive my best friend? Watch
In college: I also have a "friend" that did that to our other friend, after that the whole group dynamic shifted and they stopped talking for the whole year.
Personally that "friend" is not your friend, no real friend does that! Being drunk is no excuse, obviously don't overreact because she can turn everyone against you. She can longer be trusted because I can not fathom kissing a guy that I KNEW my friend REALLY liked (never mind sleeping with him. Girls like that can not be trusted. Seriously.
Being the vindictive person that I am, I would wait months find out who she likes and do the exact same thing. I may stoup to her level, but the satisfaction of the revenge would taste so sweet.
* * * I personally you shouldn't tell her how much it bothers you, because like other people have said its an "ego trip" for her. So her knowing how much it hurt you, she will relish the thought. SO don't bring it up, if she brings it up just shrug it off and act like it doesn't bother her. It will kill her ego