Chick with gimped leg, help with care?

Went to a local farm supply store yesterday to pick up some bird seed and they had a lot of chicks for sale. After interacting with them for a while and watching their antics I noticed one that was a bit smaller than the others in her pen and couldn't really walk right. I ended up taking her home and set up a makeshift cage for her (since she can't climb we used the bottom of a pet carrier - I put the top back on it at night just in case, but otherwise I've always got an eye on her) and though she was struggling in the large pen with all the other chicks she seems to be doing better. I have never had chickens or any kind of bird but I wanted to help her.

She eats and drinks just fine, leading me to believe she's runty because she couldn't reach the food in her pen since it was in feeders. We just hand feed her or place food on the bottom of her cage where she can get to it. Sleeps a lot, likes being held, makes lots of noise. Other than her leg she seems healthy. The attendant at the store said she probably wouldn't even make it through the night but if anything she seems even more energetic today than she was when I got her.

Can anyone give me advice on accommodating her?