Get the ivermectin pour-on that was recommended in your other thread, and put the drops on the back of her neck between her shoulders after parting the feathers to make contact with her skin. It is $20 at TSC. They are probably lice, but they could be mites. Lice eggs can usually be seen as small white clumps at the base of feathers.
You can also use permethrin concentrate, mixed with water per label instructions for chickens, sprayed on her skin with a spray bottle wherever lice are found. Usually they will be around and under the vent, but others can be around the neck and under wings. TSC sells pint bottles to mixed with water for under $10.
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