Anyone? I messaged the person that posted the pics and I was told the chicken is eating and drinking and she is behaving normally and is due to lay eggs next month. No others chickens in his flock have this issue.
She could have mites or lice, so look carefully parting the feathers for tiny reddish tan bugs, or for white clumps of lice eggs or mite dirt at the base of feathers. The damage could also be from feather picking or rooster damage. Mareks disease also has a skin type, but feather picking would be my first guess. I would get some Nustock cream to apply to the areas to help heal, and the bad taste can help to prevent pecking. If it is from a rooster grabbing hold of her neck, I would separate him for a bit of time.