She’s technically not doing anything wrong. She can’t control who has a crush on her. Just because she goes hiking with a coworker it doesn’t mean that particular coworker has a crush on her and it doesn’t mean she’s cheating. They may just be friends. She’s probably just hiking. Maybe she’s proud of her progress. She’s allowed to post those photos. At least they are not nude photos. You don’t get to control her. You are allowed to have your feelings but if you don’t like it, you can simply tell her. Maybe she will tone it down. If she doesn’t want to change her social media behavior, there’s your answer and there’s the door. You can’t hold onto these feelings and stay with her. It’ll only turn into resentment.

Personally I wouldn’t be posting my ass everywhere because I wouldn’t feel comfortable with it. I’m a bit more modest of a person. But that’s just me. It would make me feel uneasy if my spouse was having the same online behavior. But if I told him and he didn’t stop, that would ultimately be his decision. I would not be okay with nude photos though. That’s where I would draw the line.