Had a girlfriend once that got one of HER girlfriends to ask me if would I hook up with her just to see if I would take the bait. I smelled a rat and confronted them and they admitted their little scheme. It was at that point I knew the relationship had a quickly expiring shelf life. Also, same girlfriend scheduled a dinner party with coworkers at the apartment where we lived together, at that time my mom had advanced cancer, she passed away and the funeral ended up being on the same day as her dinner party. She refused to cancel it.......and that as they say, was that.
I’m glad you escaped from that mess, AND you did it before you made the mistake of marrying her.