How old is she and what breed? What type of feed does she get? Many ducklings, especially the heavy-weight breeds, need extra niacin, not just what comes in their food, just due to how fast they grow. Splay leg and pigeon toed, or turned in feet are classic signs they need extra niacin. Many avian vets aren't really used to poultry, but specialize in the exotic birds, and are a bit clueless - at least that's been my experience with my avian vet. When you have a problem the Durvet liquid vitamin B is really a miracle worker, that's why everyone recommends it here on BYC. Even if it's a birth defect it will help to strengthen the little ones legs. You can post pictures and give more information and you might get even more help.