I am SO sorry to hear about everything your daughter is going through right now, Milerprof!
I developed RSD in my left leg in 2007 when I was 12 years old after an ankle sprain. It took 4 and half months to diagnose and later spread to include both arms and I have just been told that although I have back issues, my doctor now thinks it may have spread to my back.
I've spent 13 months in a wheelchair after a nerve block caused me to lose my coordination. I had to participate in a 3 week intense physical therapy course to learn how to walk again. I'm now 16 years old and can walk short distances with crutches, not perfect but better than how it used to be.
I can't imagine how scary this must be for your daughter at such a tender age. It was soo hard for me at 12 years old but I can't imagine how your daughter must be feeling right now!

She must be one strong girl!
I agree with what the others have said, try and get her in to see either a Neurologist or a Pain Management Doctor. I live in the UK and in my opinion, Orthopaedic Doctors aren't very good at picking up on RSD. It was a Neurologist that told me he thought I had RSD and then sent me to a PM Doctor.
As for the blocks, I have only had one and I was put under general anaesthetic for it because of my age so they may do that to your daughter also so it's less traumatic for her.
My PM Doctor has always told my mum and I that he feels that RSD may be genetic or that if theres a history of neurological disorders in a family, you are more likely to develop it. It hasn't been proven yet but makes sense for me as my nanan had MS, grandad Parkinsons Disease and an uncle had an untreated chronic pain condition. My Doctor was going to do a study on it but I don't think he ever has.
I know how hard it is (as you do) but tell your daughter to keep moving as much as possible. Casting led to me developing Dystonia (a movement disorder) that I have never been able to get rid of no matter how many treatments i've had.
Don't give up hope. Keep pushing for a second opinion if you aren't satisfied. I was always told that the younger you are when developing RSD the more chance you have of it going into remission so that is working in your favour.
If you ever want to talk, please know that I am here for you. I know how hard it is to deal with all of this!

My mum would also be happy to talk to you from a parents point of view.
Take care and keep us posted.
Alison