Sorry about your duckling.
I have seen this "form" of Wry Neck before and in my personal opinion it's almost either likely due to a malposition during hatch which caused great muscular pull to one side of her neck causing the skeletal deformity you're seeing here, another good guess would be some type of genetic defect/trait that was passed on from her parent stock.
I haven't had good luck treating these types of birds sadly, but before I would do anything dramatic, I would start offering her some thiamine(B1) in the form of Cattle Liquid B Complex, and start administering vitamin E Human Soft Gel Capsules. How old is she? Looks around two weeks, but is probably older correct? You can give her around 1ml of the B complex a day, and 400iu of the vitamin E Soft Gel capsules a day.
Also, would be good to try to straighten her neck out a few times daily, and let her do some supervised bathing time.