Here are some links that you can read for more info:
https://www.backyardchickens.com/t/879233/slipped-tendon-in-chick-anyone-ever-try-to-fix-this-experiences
http://www.thepoultrysite.com/articles/1051/leg-health-in-large-broilers/...
I am not an expert on leg problems, but that looks to be either a slipped tendon or varus valgus deformity on one leg. I will send some links to read with pictures. She is a pretty cute little chick.
I use vitamins just for chickens. The easiest ones are powders added to the water daily. You can also use a tonic called Poultry Cell 1ml for a chick orally every day. Some use baby vitamins 2 drops orally every day. Vitamin BComplex tablets can be ground into the feed or water as well. Slipped...
Slipped tendon or leg bone deformities such as varus valgus deformity, tibial dyschondroplasia, or twisted legs can be very common. Chick vitamins added to the water can sometimes help if it is a deficiency.