Deal Em Eh?

Hi there. I have a dilemma :/. So, a few months back I had 1/2 ass threesome with my homegirl and her boyfriend. Yea I never really do a full on intercourse with the guy therefore it's a 1/2ass3some lol. Anyway, lately, the three of us have been hanging out and my homegirl occasionally passes out due to too much liquor intake, and her boyfriend has been feeling rather BOLD. He had the nerve to try and get touchy feely with me and expect me to just be all gun-ho about the shit. Now, it's true, every time this happens (twice) he's extremely drunk....usually vomits an hour later. Still, I know this isn't enough of an excuse. So they've been together for almost 3 years now and I know it is probably best for me to go ahead and tell her but I really hate to add complications to their relationship. I figure I just need to have a one on one talk with him and explain to him how vital it is that he never does that stupid shit again or else of course I'm going to have to tell. But, firstly, I don't really have that opportunity and secondly and I suppose most importantly if it were the other way around, I wouldn't want my friend warning the nigga, I'd rather her just tell me right off back. I don't know what to do. I hate that I've been put in this position. I really can't stand a nigga who feels like he can get away with that type of shit but I'm trying to understand that he's young and in those situations...really fucking drunk. I'm thinking maybe he just needs to be put in check....? No? Initially, my ex told me it wasn't that big of a deal for me to go and cause issues with the two of them, but still I can't help but to think if it was ME in that situation. I guess I kinda know what I have to do. Really sucks... we were all such grand buddies. *shrugs*

-Ziggy