I don't think River lacked concern, I just think it ties back with what she said earlier about having to hide the damage around the doctor.  She tried to hide her broken wrist and now she is hiding her emotions so he doesn't see how much pain she is really in.

I don't think River lacked concern, I just think it ties back with what she said earlier about having to hide the damage around the doctor.  She tried to hide her broken wrist and now she is hiding her emotions so he doesn't see how much pain she is really in.