Never done this, except cybersex. I didn’t know her husband, but I knew he was her husband and we all played an mmo together. I convinced myself that he knew and didn’t consider it cheating. Then she kept venting to me about what a bad father he was for their kid and I slowly faced the fact that she wouldn’t be trying to convince me he was bad if he knew, so I told her to keep it nonsexual from now on and she quickly moved on to another player I knew. It doesn’t feel good, especially in hindsight. If you’re ever in that position you’ll feel better in the end not kicking the person while they’re down.