Ali, you do whatever seems the best. Doctors don't know everything, and neither to Physical Therapists.
Not saying I know anything about RSD, but I suggest only taking
calculated risks. I've heard you talk before about getting the casting, and there's just no guarantee that it will help, and the possibility it may make things worse.
You and your Mum know your body best. Don't let anyone use scare tactics and bully you around.
Prayer helps. I'll keep you and your Mum in mine.