Eric, you are getting some sound advice. I would just say again: Avoid any relationship talks, and if she tries to drag you into it, don't let her. As long as she is with someone else you can't win. Watch from a safe distance what happens. Sometimes these affairs have to play-out before the WS wakes up.
Be strong
M53 H54 D17 M33Y T38Y Bomb OW 09/09 OUT 10/09 BACK 11/09 OUT 01/10 WANTS TO R 04/10 BACK with OW 05/10 Wants to Reconcile 05/11 I said NO