It can be possible for Mareks to cause the curled toes, but I am thinking the chick has riboflavin deficiency. If you Google “riboflavin deficiency in chickens,” and look for ThePoultrySite article, you will see similar pictures. It is called curled toe paralysis. I would start some B Complex vitamins 1/2 tablet daily in some food, or poultry vitamins in the water containing riboflavin (vitamin B 2) right away. Hopefully it will help, but it doesn’t always work when it has been going on so long. I would not tie the legs together, but Google chicken slings for pictures. You can make one easily, and place food and water near. Let the chick out frequently to stretch, and for you to do a little physical therapy. Marek is possible, but usually affects older chicks. I would get a necropsy done if you lose her.