Men, What is she doing on a date with another man on her mind?

She wanted him to meet a bar manager. This came just as they were making up after a long period of martial strife. The bar manager is the boyfriend of her divoree' friend. Husband found out they and bartender's buds were drinking together on the "girlsnight" at her friend apartment. When he said he'd confront the guy, she changed her mind. Said she didn't want him mad at the guy. How do I get through to this him something's going on? Opinions?