Hi Angie,
I'm sorry to hear you mother is having trouble. Seeing a physio definitely sounds like a plan, although to see improvements will require effort to do the exercises to correct posture, regain range of movement and strengthen the area. Sleeping with a rolled towel under her neck at night would be good as well to try and avoid her assuming any aggravating positions.
I see you mentioned a neck brace above. That the sports doctor laughed I agree is not nice at all, and could definitely use some work on his interpersonal skills! However, for management of neck problems here in the UK I think neck braces are avoided where possible, as immobilising the neck is thought to increase stiffness and pain further. I did a quick search and found that evidence is as usual conflicting, however many papers advocate exercise over restriction. I have attached a paper which provides somewhat of a summary on whiplash - although it is now 6 years old and is by no means definitive (i didn't have access to newer ones), it does discuss some of this issues in the development and treatment of whiplash.
Hope this was helpful and good luck with it
Rachie