He was foolish....spoilers
She meets up with her ex husband at the airport after spending the night with Jean-Baptistery and suggests to him that they do a bit of traveling before they head home. They then get back together. She never bothers to apologize for leaving him earlier for Jean-baptiste when she had to know he was hurt by it.
Her sleeping with Jean-Baptiste ruined the movie for me. Up to that point it was corny yet entertaining. The writers would have done well not to include that in the plot and the movie might have been better received. But since she did sleep with him my feelings were that I wished he hadn't gotten back with her and he was foolish for doing so.
After all they had been through together and her knowing how he felt about her, she dumps him at the dock for a rich and much younger guy whom she hardly knew and then slept with him. She knew she was hurting her ex husband when she left him for Jean-Baptiste. She acted like a gold digger and a cougar. She tossed aside any feelings she might have had for her ex husband to be with a younger guy. Her ex husband knew she didn't return to their hotel that night so he would have been better off without her especially since they had recovered the money.
He should have told her to go back to her boy toy.