I would try to give her some vitamins—400 IU of E, some thiamine or B1, and a bit of egg for selenium. Thiamine is found in a lot of foods, such as liver, hamburger, salmon, sunflower and sesame seeds, and plain yogurt. B complex, nutritional yeast, and chicken vitamins also have them. Her movements in the video look a bit like wry neck with her neck twisting to the left, and backing up. Wry neck is just a neurological symptom, and can be seen with a head injury, a vitamin E or thiamine deficiency, in certain diseases (such as Mareks and others,) that affect the brain, and it can be hereditary in some chicks.