Last friday I was at a party where I met this girl (we had seen eachother before, never talked tho).
At one moment after talking a bit we started dancing pretty close, she grinding me and grabbing my head. When I tried escalating she said she had a boyfriend and she couldn't cheat on him, but she also said she would kiss me if she was single.
Since we were both pretty drunk we ended up kissing anyway. A friend of me came and told me to stop so I did and kinda ignored her then until she left.
I kinda like her though and was thinking about seeing her again so I added her on facebook and she accepted, but I'm clueless about what I should say now, should I apologize about trying to and actually kissing her? It will probably be hard to say hi and not mention what happened

Or should I just drop it and move on since she's with someone... (she cheated on him before once so I don't know how healthy their relation is) I'm pretty clueless!
Any help would be appreciated, it's the first time I've had to deal with women who aren't single!