This chapter felt kinda like a waste. Nothing about "she smiles around miyabi" means she is unhappy around them, nor that she won't smile with them (he even realized she is happy among them too). But more importantly, nothing about hanging around them prevents her from also hanging around her latest crush. All they have to do is extend the invitation towards him, too.
Besides, whether someone smiles or not is a bad indicator as when someone is focusing on their work they will have a "gameface", which will look rather pissed off by default. That she was around miyabi whenever she had a break and thus engaged in making merry with her latest crush, will obviously be correlated to smiling. While when talking with him she was usually in work-mode (or assuming he addressed her for work), so obviously she was going to be serious. He should have been looking at her face when they made camp and were just talking, instead.
Or, yknow, just ask her outright. She is an adult, giving her the option to join their party is fine, she will be able to make her own choices. Particularly if you make it clear she should try to maximize her joy and merry.
Besides, whether someone smiles or not is a bad indicator as when someone is focusing on their work they will have a "gameface", which will look rather pissed off by default. That she was around miyabi whenever she had a break and thus engaged in making merry with her latest crush, will obviously be correlated to smiling. While when talking with him she was usually in work-mode (or assuming he addressed her for work), so obviously she was going to be serious. He should have been looking at her face when they made camp and were just talking, instead.
Or, yknow, just ask her outright. She is an adult, giving her the option to join their party is fine, she will be able to make her own choices. Particularly if you make it clear she should try to maximize her joy and merry.