It certainly looks and sounds like Marek's from your description. If she is still eating with enthusiasm then there is a chance that she can make some level of recovery. I had one that was nest bound for a couple of months but eventually got back to free ranging with the flock and laying eggs but retained a limp. She flew to keep up with the flock when necessary. The rehabilitation was slow and ugly at times to watch as I would encourage her to make her way over short distances towards a focus, like a treat or the chicken coop at dust. She would crawl using her wings initially but over days and weeks she managed to re-coordinate her legs until she could eventually hobble 40 feet to the coop and she could get up onto the highest 6ft roost. Sadly, I eventually lost her and her sister to a fox, but she had a very good and happy quality of life despite her disability and she was a total pet due to all the handling and care I gave her, so she would come running/flying when you called her. Yours is a slight bird and that may work in her favour if she is to recover, because flying will be easier and less weight on her legs.
If you haven't made one already, a chicken sling is good for keeping them supported in an upright position and can be made out of everyday items....
Pots for food and water can be clipped to the front so that she can reach them to fed herself. I would recommend a good quality vitamin supplement like Nutri Drench or Nutri Drops to support her immune system and good food and probiotics to support her gut. If she loses interest in food, then that is the time to euthanize in my experience. Sunshine and grass and the company of other chickens in a safe environment like a large dog cage are the things that seemed to make the most difference in turning things around for the birds that made recoveries in my flock. Stress is to be avoided at all costs because they get flustered and that makes them worse. That is why getting them to move towards a focus or goal like a really nice treat is the best physio, without being handled or jostled by other chickens.
It is possible that they were infected with the disease as day olds but unlikely unless they were broody reared. The disease does not transmit vertically through the egg but has to be contracted by the bird after hatch and does so by inhaling infected dander dust. Being hatched in an incubator the only exposure would be via transfer on skin hair and clothing by the "breeder" from their flock. If the incubator or brooder were in or near the coop/flock then that increases the chances.
If they came from a hatchery, it is unlikely.
Watching & learning, thank you all for sharing your knowledge 
