Invite him over to your house for drinks, tell her he's coming over for drinks and that she to wear a really short skirt and a low cut top, no underwear and watch them fuck
My guess is that while you were pressuring her to become a hotwife she may have tested the water behind your back and fucked her coworker. The same guy that you agreed she could fuck which was magic to her ears as she could then fuck him without fear of being caught. Another guess by me but I...
Your right about the trust and communication wins the day, but she was the one that was push into having sex with her co-worker by her husband, then after she finally agreed and put herself out there, hubby pulled the rug on it at the last minute. In my opinion it had gone too far for her to...