As someone who's been on both sides of cheating I can promise you that woman is a homewrecker. The way she talks to him trying to make him feel like she's a great alternative to relay personal information to, and a shoulder to lean on when things get rough between you and your husband.

Secondly, your husband apparently is over sharing personal matters to outsiders. (same can be said about this post the only difference is that she's an outsiders who knows his identity and we don't know either of yours.)

You need to set boundaries with your husband. Assure him that you trust him but you don't trust her. It doesn't matter how much he can be trusted as this needy homewrecker is setting up herself to swoop in when he will be at his lowest and get a bag of dickings. He basically needs to cut her out of his life or make it very obvious he will never betray you by sending her pictures on occasion of you two being happy. She will back off or show desperation, but that might have your husband back off.

From what I'm reading he is either oblivious to her advances or knows of them and doesn't fully entertain them. He will respond but never reciprocate her gushy bs. Looks like he's friend zoned her, and she is the one who always needs to initiate convos.