How unwell does someone need to be to say a refuah shleima for them?
For example, is it permitted if somebody had a serious virus and although they no longer have it, they are still recovering and very weak and tired?
For example, is it permitted for a pregnant woman who is tired and weak from the pregnancy? Tired and weak to the point where it makes life harder, although not seriously or dangerously tired or weak.
There is nothing wrong with blessing someone that they should feel better, or beseeching H-shem to help them feel better. Additionally If the person is still weak from a virus, he has still not recovered. The same with a pregnancy, if she is weak, there may be good reason for it, other then the regular pregnancy symptoms, and you can surely bless them, but even if it is the regular, there is nothing wrong with blessing them that she should feel better.