Did you witness the injury? Is the foot or leg paralyzed? How old is she? I would rest the foot in case it is broken, and let it heal.There could be some nerve injury due to the injury. Do you have a rooster? Do you think that Mareks disease might be a possibility? I would continue the vitamins for a couple of weeks. Can she get around at all? Make sure that she can reach food and water. Consider making her a chicken sling. Here are some examples, especially in posts 5, 11, and 12:
https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/t