This dilemma is so tricky because your loyalty to your friend can pull you in two different directions, says Greer. On one hand, you don’t want her to be with a dude who gets frisky with her girlfriends. On the other, you want to protect her feelings. One way to decide whether you should tell her is by being honest with yourself about her personality. Does she always, in a very self-assured way, joke about how flirty her husband is? Has she tsk-tsked cases of celebrity cheaters, saying she could never be with a man who didn’t only have eyes for her? Does a green-eyed monster lurk right beneath her surface, or would she not bat an eye if a Jennifer Lawrence lookalike hit on her husband at a party? If you know her really well, chances are you’ll instinctively have a hunch about whether she’d want to hear about what happened.