This "couples" friendship is clearly over.  The writer may be able to continue a one-on-one friendship with the other wife, but it will be uncomfortable.  From my own experience, you can't win whether you tell her or not.  The first time this happened to me it was the husband of a dear friend when she was out of town.  I told her about it.  She either decided that I was lying or that it was my fault, and ceased being my friend.  The second time it was the partner of my long-time best friend.  I didn't tell her.  I figured she already knew what a skunk he was (everybody else knew it) so why should I add to her misery?  Later after she caught him in an affair with another woman and dumped him, I confided in her.  She was furious that I hadn't told her at the time.  She forgave me and we are still friends, but it just proved to me that in these situations one is absolutely between a rock and a hard place.