Her food is supplemented with Niacin. I had a phone consult with an avian vet today who said she thinks it's a birth defect, but they're not seeing waterfowl in person because of the flu risk so she couldn't advise me how to wrap it or isolate the joint. I'll check out that other thread, thank you!There are lots of threads on BYC about pigeon-toed ducks and how to help them. Here is one: https://www.backyardchickens.com/threads/3-week-old-ducklings-legs-turned-inwards.1583360/
Definitely get her started on liquid vitamin B complex ASAP! 1 ml every day over treats.