I can understand what your mother is going through. I can not stand, nor walk either due to the neck pain. I was able to get a handicap parking permit with my doctor, and this does help when I'm out and about.
If the doctor is not helping or trying to figure out what is causing this pain, it's best to move on and find another doctor. A pain management clinic would really help control the pain while your trying to figure out what is causing this pain. I wish you and your mother the best. There are muscle relaxers that will help ease the spasms.
Has she seen a pain management specialist... to help with the pain while she recovers and/or goes through PT?