With Circles of friends, when they are in a D+M it is advised to steer clear of them until it is finished unless you are definitely sure you're sure of the topic and it geneuinely relates to you.
If unsure ALWAYS check with someone else within the group of friends, who is NOT participating in the D+M to check whether it is ok to approach them and talk.
Guy B: Oh, he's in the kitchen with Katie having a D+M about there relationship
2)GuyA: *walking over to friends in club*
Girl A: *seeing the two friends are in a D+M* Woah, leave them a second, this aint our business