my friends husband has a relationship outside marraige

I don't know. My husband recently told me that he is seeing another woman. Funny thing was I was mad with him for a day and then I was calm. He was afraid that there was a storm brewing. He has told me everything about it since then. If I asked the right questions, he would answer me truthfully. I'd rather be told the truth from him rather than from anyone else. And I definitely would not want to find out years later about it. But for your case, I'm not sure how she's going to handle it. Different people will react differently. Try breaking it to her gently. It's hard to accept these things. Maybe start asking why his husband is not home early lately or something like that, I'm sure there are tell-tale signs she is ignoring. If she gets the hints, she may ask you if you have heard anything. Then maybe you can tell her. I don't know. It's tough. I'd rather know than be ignorant. I have heard of incidents where relations outside marriage has been going on for years and yet the wife did not know. I can't take that. It would have been too painful.