In case anyone reading this is going through a similar experience as I have, here are my final thoughts on the matter.
There are differences between men and women. For a lot of men, it would seem very easy and obvious to stop an advance, all you have to do is say "Fuck off" or give them a push. I'm not sure its the same for all women. If a woman is heavily intoxicated, finds herself alone with a man, how easy is it to get out of that situation? Some women, sure, its easy for them. But some women are hard-wired all their life to feel a (false) sense of obligation to men. And if you're dating a very attractive woman, as in my case, they are constantly being hit on and chased by men... What a world that would be. This is why boundaries are so important for women.
If your girlfriend comes to you with something like this. Give her the benefit of the doubt. Then do your digging, get your re-assurance, and talk to people, because I'm sure there are some women out there who abuse this grey area. That's not OK. That said assault and rape are unfortunately super common (the statistics are shocking), and overwhelming with female victims. We will never be living in that world as men.
I do consider what happened to be sexual assault. I don't believe someone in a blackout can consent to sexual activity. It would be different if they got drunk together, and consent was provided before intoxication. But in this case, this man found my blacked-out GF at the end of the night, and took advantage of her when she was not in a state to make any decisions about anything. She was uncomfortable, she stopped it, and she did not want to be participating in that. This guy knew she was vulnerable, he made sure to get her alone, and then he did something extremely slimy.
Some people will never understand this because not everyone has experienced a blackout. But in this state, you are not picking up on red flags, because you are not making memories (short or long term). If you are in a blackout state and someone grabs your ass, and then 10 minutes later asks you to walk home, you likely don't even have that memory of him grabbing your ass (red flag) and thus can't make an informed or safe decision on whether this is a guy you should walk home with. You are essentially in a state of amnesia. See a great quote by malcolm gladwell below.
"And what is the consequence of being blacked out? It means that women are put in a position of vulnerability. Our memory, in any interaction with a stranger, is our first line of defense. We talk to someone at a party for half an hour and weigh what we learned. We use our memory to make sense of who the other person is. We collect things they’ve told us, and done, and those shape our response. That is not an error-free exercise in the best of times. But it is a necessary exercise, particularly if the issue at hand is whether you are going to go home with the person. Yet if you can’t remember anything you’ve just learned, you are necessarily not making the same-quality decision you would have if your hippocampus were still working. You have ceded control of the situation."
— Malcolm Gladwell, Talking to Strangers: What We Should Know about the People We Don’t Know (2019)
Bottom line, there is a huge difference between just "being drunk" and being "blacked out". And because of this, like so many have said on this thread, nobody should drink to this state. In the case of my GF, this is not an established pattern of behaviour, and she has drastically transformed her life over the past 6 months as a result of what happened. That means a lot to me.
If anyone is going through something similar, I will say this. I think you are within your rights to dump your GF/BF after something like this, but don't do it for the sexual actions, do it for the drinking.
Also, take the advice of strangers on the internet with a huge grain of salt. Nobody knows all the nuances of your situation, and only you can make the decision on what to do. Talk to your friends, family, therapist, and listen to your heart.
[This message edited by rothman9499 at 3:44 PM, Wednesday, March 1st]