Those look serious. Start out with a daily warm Epsom salts or soapy water soak to her legs and feet for about 15 minutes. An old tooth brush can be used to gently scrub the scales. Then dry her well. Apply a thick oil such as petroleum jelly to the legs and feet rubbing it well under the scales. Nustock cream for horses is also good to use since it contains sulfur and oil, and will kill the mites. There are many methods for getting rid of leg mites. Make sure the hen is using a dust bath since that can help keep parasites off her.