Wry neck or a droopy neck cannbe a sign of a head/neck injury, a vitamin E deficiency or can be a neurological symptom of something like Mareks disease. She also might be dehydrated and not getting enough food due to her low pecking order. I would place her inside a dog crate with her own food and water within the flock, so they can still see her.
I prefer not to separate away from the flock, since a picked on chicken, will be harder to get back in the flock.
I would offer her human vitamin E 400 IU 1 soft gel orally once a day. Just pop it into her beak. Feed her a little scrambled egg and moistened feed. Human vitamin B complex 1/2 tablet daily crushed into a spoonful of water or in food is also good.
I am not a fan of scratch and peck feeds since they may pick out the most desired parts first, and deficiencies can occur. Sometimes the vitamins or minerals are just powdery and can be left behind. A homologous layer or all flock feed, either crumbles or pellets, would be less likely separated, and each bite would be the same. Let us know if the vitamins help her.