Sounds like she may have broken her leg or slipped a tendon. Check the bird's whole leg for signs of purple and swelling, especially in the calf of her leg. If you see that, make sure to isolate her from other birds and stabilize the leg with tape and sticks. I have had this happen once, and not...
I had this happen as well, hatched 5 tiny, runty white coturnix quail that developed slowly and had health problems. Turns out they were albino! If you look at the bird's eye, does it have a reddish pupil with a blue sclera? This would mean that it is albino, or leucistic at the very least.
