Can you get photos of her poop?i feed them layer crumbles and scratch grains
I agree, I would get some Permethrin and treat her, the rest of the flock and their housing as well.
You want to get rid of the bugs.
She's eating layer crumbles and scratch grains, since she's not laying eggs, I would feed her chick starter or an all flock feed. Cut out the scratch grains for a while and focus on her eating a nutritionally balanced poultry feed that is 18-20% protein.