When I am concerned about someone, I just say other stuff. My sister also has mental health issues, and if she texted me that she hadn't showered in 6 days, I would inquire as to why and more importantly, when her next appointment with the psychiatrist was scheduled.

I don't think anyone ever really knows anyone else. Regardless, the therapist is not a new person to me.

I'm not sure I'm overthinking so much as trying to understand. It's not that I've never heard the expression before, but it didn't really mean anything to me then, either.

I talk to very few people. I text with my sister some. I write stuff on this forum. I occasionally have brief interactions with my roommate. I infrequently have to chat with the parents. I don't have a whole lot of experience with people saying things to me.