Ironically this story is almost exactly how I got into my first group sex experience ...
I was 17 and the guy I smoked up with regularly invited over this little college tart. She was HOT!!!! 5'4" with perfect curves and nice perky little breasts.
Well after she started smoking with us it became obvious she was one of those horny smokers. Well my friend being in his mid 20's knew a hell of a lot more of what to do with this situation than I did.
For several months we'd get fried on Saturday night and after about an hour of being stoned they'd start making out and then gravitate towards his bedroom. She was a screamer and he wasn't all that quiet either. After about 3 months of this I got sick of getting high with them only to be left alone with some movie while they got busy.
One night after they left I fired up the bong again and took myself MANY tokes over the line to build up courage. Once I could barely find the floor I stormed into the bedroom (the door wasn't ever locked, this should have been a clue) and demanded, "Listen this has been going on for months and I'm sick of sitting on the couch while you to fuck like bunnies, this shit has got to stop or I'm not hangin' with you guys anymore!!"
She rolled over and massaged her breasts and said, "Shit I can't believe it took you 3 months! We've been waiting and I've been wanting to get your high school ass in bed since I first came over. Get over here and fuck me or get out!"
That ended up being one of the best summers of my life up until I met my wife to be 2 years later. So as this OP's story goes, it sound VERY similar and if I had friends pulling this shit I'd sure as hell get the clue.
Ironically my 'other wife' and I did this to her husband and my wife last month, we were all stoned but she and I were both horny and started going at it while they were half watching half sleeping through a movie. Eventually everyone joined in and a good time was had by all. It's not really rocket science but those of us of the male persuasion tend to be a bit dense, even when the signals are obvious. This falls under, "If I knew then what I know now" kind of thing.
-RT76