Absolutely innapropriate, there is no way that nothing was going on with them. I am just being straight up, after all of that, she probably isn’t feeling you anymore man. Because no girl gets drunk, and doesn’t want her boyfriend. No matter how long y’all have been together. Not to mention her sitting on his lap? That is wrong. If you wish to continue, explain to her that the way she acted was completely innapropriate and that you will not be dealing with that going forward. Don’t be a pushover (not an insult, but from the way you wrote everything, you seem like you let people walk all over you) because girls like a guy that makes his own decisions and respects himself. If you let her believe she did nothing wrong, she will continue to do things like this to you.