The legs appear to be in good shape, and with that, you say there apparently is no abnormal signs to indicate otherwise. This may suggest neurological motor function is being altered in some way. Neurological trauma, bacterial/fungal/viral infection, parasites, heavy metal poisoning, nutritional deficiencies, and, or metabolic diseases are all possibilities.
Out of all of those she is already predisposed to neurological damage since from what I gain she I being housed with turkeys. Oftentimes they'll peck ducks in the head, have you seen that behavior recently? Unlike other conditions mentioned, oftentimes birds with neurological trauma will go from completely normal to short spasms. Stress can promote such problems, so some days are better than others.
Unfortunately, determining which of the problems may be the culprit often relies on diagnostic tests done at a vet office; however, in some cases just nutritional, and supportive therapy can help reduce, and sometimes resolve the problem. Given her current state, it may be best if you make a pen for her so she can be separated from the flock, but see everybody else. Starting her on B vitamins, specifically thiamine (b1), and vitamin E, may be beneficial fr neurological health. From the video, her eyes appear a little gunky (likely associated with debris accumulation correlated with lack of bathing) thus said, ensure she gets in deep clean water at least once daily, the more the better.
