No feather loss, she is free ranging but I have dogs, including ex rescues and meat would be found by them long before the chooks! That said, she could definitely have found some maggots, they are free range. Its not a total paraysis, she could move her legs, they just wouldn't hold her.
She is seperated and will be so until she can stand and walk, she is better than she was, but not having some instant recovery.
I dont' think its Marek's.
Would she have some movement if it was caused by maggots?
Is there anything else that can be done for her if this is the course.... she is having some human antibiotics...