I've broken up fights between two female friends...not a bright idea..but I was real close to em, one of em struck me...i didn't respond cause uh a 6'3'' dude hitting a woman back wouldn't be a good look
I haven't broken up a fight between male friends...from my experience it only occasionally gets physical....
and I don't get involved with couples..unless I sense there is some severity, e.g. I learn that there has been some problems...I know how to get involved without making things dangerous.