Is it cheating if she has sex again after foursome
So I (m32) recently had a foursome with some close friends and my gf (f26). I knew the girl (L I'll call her) in the relationship since I was a teenager and her bf for a year since they started dating. We had some drinks, maybe too much but we had agreed to this before when we were sober. Anyways, we have the sex all of us and there weren't many boundaries, basically don't finish in each other's SO and respect consent ofc. However, we finish (1-130am) and we have more drinks and play some board games and I even do a drink/food run with L. So we all go to bed maybe 3am and we are pretty drunk at that time, however I wake up not long after and L is fast asleep but my GF and L's SO are gone and I go into the kitchen and they're having sex again. I was still drunk so I watched for a minute and then went back to sleep, pretty sad but kind of turned on. (I might have a cuck kink idk, not the purpose though). I'm not sure if he's finished inside her either. Lastly they don't know each other, this was their first time meeting. I haven't told L and my gf hasn't brought it up, so I'm asking if they have sex after the 4some ends but it's the same night, is it cheating?
Update 1: I texted L and she called me immediately after she read the messages, I just detailed what I saw. She asked for more, I told her basically what I've told y'all. She asked to meet up, but she feels the same way I do, more sick and confused, unsure if this counts. She said her bf didn't say anything either. My GF is here with me but I haven't said anything yet, I'm staying with my brother because my GF and I live out of country so I'm waiting for him/his family to go out for a hike to say anything.
Update 2: I spoke to my gf, she admitted before I even got it all out. She said: first she's incredibly sorry, she didn't know what the rules are and she was pretty drunk and went with what he wanted. They started because she went to the bathroom and he went out to smoke and they ran into each other, he put his arm around her and she said not right now but he kissed her before she finished and she kind of went with it. They had sex for maybe 15 minutes before he finished, he finished inside and told her was going to she tried to push him off hard but he's strong she was on the counter and him in front of her so he had leverage, so he finished. I asked if she felt this was SA and she said no because kissed him back. (Her words) she's upset and wants to talk to L about it too. - follow up she's East Asian and English is her second language so sometimes it's difficult for her to communicate.
Update 3: Sorry, obviously been talking this through with my SO and L. I'm not going to go into specifics but here's the keynotes: I decided to be there for GF first and support her, I told her I think this was cheating and we need to address that but now I'm here for her. L came over and we talked it all out, she was upset and crying too, she will get the BF side but I think she's going to dump him. Like 80% sure. Some context: GF and I have done sexy things like strip parties and shibari before, even drunk, she's always been on ( not infantilize it) good behavior, so I believe her every word. We've dated for 2 years when she started grad school and I started my PhD , and I care about/trust her. When we get back to her country we will start couple counseling and she's gonna find a therapist for SA survivors. She maintains, her words as I interpret them, that it was SA-adjacent, she doesn't want to go any farther with it. This went to a dark place and I'm not super comfortable going much farther on this. Last update will be 4 and it'll just tie up what happened with L and if my GF pursues survivor therapy. Ngl I feel bad, like my lack of immediate rage allowed the SA to happen, I'll probably have to work through that too.
Thanks those of you who answered honestly and helpfully, even if I disagreed with you. Y'all make the internet a better place.
Update 4 the BF admitted to his actions, apologized, and was dumped. (All this from L) he said he thought it was like “freeuse” all night and claimed that he thought L and I messed around while getting the food/beers. He made a move on my GF while we were out but she had said she wanted to wait (she confirmed) until I was back, but when everyone was together again it was a maybe. (His words, she says she said “I want to for [me] to get back before anything happens”). This was reported by L. GF doesn't think therapy is necessary rn but we will see, it's her choice. Finally she did admitted she could've been more definite in her no, she wanted to do it again (she says generally not him specifically) and didn't know the rules so she hesitated and said “not now” but he pushed her up on the counter and kissed her, with his hand down her shorts, she just went with it.
This is the last update, pretty sure GF and I are not gonna make it after this, but I'm going to stick around a few weeks to make sure she's fine mentally, but I don't think I can stay after her confession.