Okay, she does have scaly leg mites, so I would soak her legs in warm soapy water and try to gently scrub her legs and feet with a toothbrush to lift the scales. Then dry her, and put some type of oil on her legs and rub it into and under the scales. This might be better done when she is in a sling, but even if you cannot bathe her, I would oil her legs once a week to smother the mites. Oils to use—castor oil, mineral oil, Crisco shortening, vaseline, or vegetable oil.
It looks like she could have Mareks disease or something internal, such as an infection or tumor that is pressing on her sciatic nerves. Does her crop empty over night? Feel it to see if it is empty and flat, full, hard, doughy, or puffy. I would try making a sling. There are many inventive pictures for all sizes of chickens. Make something where you can insert water and food cups in front of her. You could also keep her positions on rolled towels for her comfort.
If you put her down, you may want to get and necropsy from the state vet to look for Mareks.