She looks to have wry neck, but if her lower body cannot move at all (if feet, legs, and wings are flaccid,) it could be botulism. Botulism from eating a toxin is common in ducks, and it starts with flaccid paralysis in the feet, moving upward in the body to the wings, chest, neck, and eyelids. Usually it causes a flaccid neck, hanging down on the bround, so I am doubtful that this is what is happening. Just tell us if she can move her feet or wings.
There are different types of wry neck, such as the when the head is down, turned to the side, but when it is up, it is called opisthonatos or “star gazing.” Wry neck is usually a neurological symptom of vitamin deficiency, head injuries, or a disease, such as certain viral or bacterial diseases. Most treat wry neck with thiamine (vitamin B1,) 400 IU of vitamin E, and a tiny bit of selenium, found in some egg. If you can use a few drops of Poultry NutriDrench, that has all 3 plus other vitamins. You could then try to use a vitamin E capsule 400 IU daily added to a treat or some egg.