Does your BFs cheat partner's know they were banging? I love when they say "I changed" like they can change overnight. He is delusional. Did you ever discuss why he cheated? Besides that, she was there. How is he changing so the scenario doesn't happen again?

If your spidey senses go off while on vacation, you end it. Let the spouse know what wonderful, supportive, and loving wife he has, and what POS her best friend is.

Be prepared to leave to leave if you have to. You don't deserve this.