So here is some more information:
Marek's disease (MD) is a common disease of backyard chickens that is caused by a herpesvirus. The virus causes proliferation of lymphocytes, a type of white blood cell found in various tissues of the body, and is often described as a virally induced cancer...
I’m almost 100% sure your chicken may have Mareks Disease. Your hen sounds like she has all the symptoms. I will be back soon to give you more information! Sorry!