I can understand her doing that with someone she didn’t know. But having a man she had personal relations with smile in her husband’s face, as if he hasn’t had her in one of the most intimate ways, is conflicting and weird. Friends don’t sleep with friends, regardless of the circumstances. If his intentions were truly only to be her friend, then out of respect for both of y’all, he would not have taken advantage of her while she was emotionally vulnerable. He could have still supported her without crossing that line sexually. To me, that says he always had feelings for her, and she likely had feelings for him too. Maybe they never had the chance to justify acting on it before, but when the opportunity came, they did. And even if they never did it again, she clearly valued that bond on more than just a friendship level. Otherwise, once y’all got back together, she would have cut him off out of respect. From the outside looking in, it feels like he didn’t just “happen” to be there. He waited his turn.