@jca – here’s what I’m thinking.
If and ONLY if she’s not sure how this friend would take it, here’s how I would steer a conversation. I’ll script this like it’s a play, let’s say Cindy and Bob are the couple, Janet is the friend. Bob hits on Janet, and Janet doesn’t know how Cindy will take it.
Janet: “Oh Cindy, I have to tell you about this, it’s unbelievable. OK, so I have a friend who’s friends with this other married couple, so one day my friend is over at their house, the wife leaves the room and the husband starts coming onto her big time.”
Cindy: “Oh my God, what a sleazebag.”
Janet: “I know, but here’s the worst part. So my friend tells the wife what her husband did, and instead of getting mad at her husband, she freaked out on my friend, called her a slut and told her to mind her own damn business.”
Now, does Cindy say, “Yeah, if Bob was doing that, I’d tear his nuts off…I certainly wouldn’t shoot the messenger,” or does she say, “well, you know, sometimes things go on in private and people get a little defensive when others start poking into their private lives, I could see myself getting mad if that were me.”
Now no conversation is going to happen EXACTLY like this, but assuming Janet signals clearly that she would want to know and that she’d take out her anger on the appropriate person, then Janet can say, “Cindy, I have something to tell you. That story, I made it up to see how you’d react, because…I’m sorry, this is hard, but when I was visiting you and Bob, Bob told me next time I visit I should leave my boyfriend home so he and I could screw around and I had to find a way to tell you without destroying our friendship.”
Now not everyone could pull that off, but you’re trying to get at a person’s core values, their own perspective, and sometimes to do that you have to present hypotheticals. It can work, but yes, you can confuse the other person if you’re not careful, you just have to know what you’re trying to achieve and stay on focus.