Crazy how serious she is taking this, I think I would have laughed about it in the morning. You don't really want to associate with someone like this is they are so easily offended. I appreciate that it is their bedroom and he had no right to be in there but he had no self control due to alcohol. He was completely out of it and sounds like he didn't know back to front. I would say this should be the main concern.

Maybe buy them a little gift to show how sorry you are but I'd probably take a step back and leave them to it. What your partner did is definitely something I'd end up doing when blackout drunk. God I've done some embarrassing things!