I would not hesitate to start something with riboflavin in it, since vitamin B2 deficiency has to be treated quickly to be successful. Beef liver chopped finely, plain yogurt, nutritional yeast, and B complex tablets all contain riboflavin. Even though your feed may be balanced and no other birds have symptoms, they can inherit B2 deficiency. There is a good link that you can read by The Poultry Site on "riboflavin deficiency in chickens" if you Google that. Curled toe paralysis is the term that they use for it. She almost looks like a splay legged chick, so she might benefit by a hobble, getting the legs closer together about 1 1/4 inches apart with a bandaid or vet wrap tape. You can also make a shoe for the curled toes with tape and cardboard on the foot.
I had a 3wk chick out of 38, develop the same problem, totally agree with Eggcessive! I purchased PolyVisol (w/out iron) Vitamins, fed the chick 3 drops to the beak 3x day, fed it boiled egg yolk mixed with it's crumbles, taped it's toes (from what looked splayed turned to Curly Toe Paralysis). Use a towel/carpet to line to bottom of it's enclosure, gives it traction. Seemed like forever but checking my notes it was about 2wks!