DWW: Mary-Beth Slept with a Married Man

So Mary-Beth did a bad thing. She slept with a co-worker who was married. Here's the crazy part: she KNEW he was married! David admitted that he and his wife now have a marriage that is "non-exclusive" and they've never been happier. Mary-Beth figured he was telling the truth, but she wanted to be sure, so we checked with David's wife. Did she CONFIRM this "arrangement", or did we just EXPOSE a cheater??