Welcome to BYC. She could be suffering with pododermatitis or foot pad dermatitis which is basically scalding of the skin from damp bedding and droppings. I would remove the straw and replace it with either pine shavings or sand. If there are any wet spots, try to fix them. Bedding should be dry and clean. Raking it daily helps to dry it out. Hay and straw tend to hold wetness and can harbor mold which is bad for the lungs and can cause respiratory diseases. If you have a dog crate, I would place her in it with food and water on a puppy pad or some fresh bedding, and place her with her flock outside during the day, and inside at night. You can try some epsom salts warm soaks to her legs once a day, and then apply some Nustock cream to her legs after each bath. Have you noticed any leg mites in the other chickens? Loose scales on the legs are usually a sign. She may also benefit from a poultry vitamin with trace minerals in it in her food or water daily. Sometimes a biotin deficiency can cause skin irritation on legs.
