Find a thot on tinder to go with you (extremely easy if you are offering a beach vacation like that), let your girl think she is going, wait until the day before while her bags are packed, then dump her and tell her to fuck off because a prettier and younger girl is going with you. She is old news. Don't even let her know you knew about the infidelity, let her feel the way you felt. Betrayed and inferior. That is what I would do.
Find a thot on tinder to go with you (extremely easy if you are offering a beach vacation like that), let your girl think she is going, wait until the day before while her bags are packed, then dump her and tell her to fuck off because a prettier and younger girl is going with you. She is old news. Don't even let her know you knew about the infidelity, let her feel the way you felt. Betrayed and inferior. That is what I would do.