Search Results: sleeping with his best friend

So, I have quite a large friend group, some people fell out, but I'm still close with all of them. Earlier this year, I saw two of my friend's whispering to each other while we were all hanging out (about 6 people), so I asked what they were talking about.

One of them was kind of hesitant to tell me, but eventually revealed to me that she was not sure if she was raped. I did understand why she felt that way towards me because the guy who was involved is easily one of my best guy friends and is pretty close to me; I go to breakfast with him, I've slept at his house, all of that. Not to mention I am one of the few people left in our friend group who still likes him (different story).

Basically, they were both drinking at a party and ended up sleeping together. Nobody thinks he has recollection of the event, but she does and feels violated because she couldn't give consent.

This is where I'm confused because he couldn't either? So, did they rape each other? Was it okay? But then again, I'm not sure if he was as drunk as her and knew what was happening. He really doesn't seem that type of person to rape, but she seemed very bothered by it and was confiding in people. She told me she doesn't expect me to pick sides, but sexual abuse hits home for me, but i also feel as if I don't know the full story to make a judgment call to simply take her side.

Can someone explain what the deal is if both people are potentially drunk? And should I take a side? I don't want her to feel as if I'm not supporting her, but I don't know...