Her toes are really necrotic, and she will probably loss all or most of them. Chickens can get around on healed stumps, but she may have problems roosting. But it is admirable that you are trying to save her. I would make sure that she is inside where it is warm, and do a daily warm soak of her feet in Epsom salts or Hibiclens/chlorhexidene and water. Do not wrap or put dressings on the toes or feet. Use a soft clean towel for bedding. It may take a month or so from the frostbite date for her to lose toes.
