Before you get sucked back in yet again, reread your post and see this is yet another circle she is traveling in, and honestly, don't we all feel good after a party, drinks, and sex??
You better think a bit about what you do next as I believe the other her will emerge again, and want space.
I think your feeling are still so intense, it clouds your judgment, and you have hope (AGAIN) she has changed, based on nothing more than words, that have no actions, and drunken sex is not positive action.
I WOULDN'T BE AT ALL SURPRISED THAT SHE SHOWED UP AT THE PARTY JUST FOR YOU. So no defending her. Just pay attention, as I know how hard it has to be to cut those kind of long term attachments and rewrite the intense history of the past, but sooner or later, you will have to make up your mind to get back into the old limbo you have worked so hard to escape, or run your own program that works for you.
No more going with the flow and being confused. Decision time. Now make one!! And stick to it!! (let the glow of alcohol and sex settle down first, because I know you needed that shot of a$$, but don't let it be a factor in your decision).
I would have left at the sight of her.