My chick doesn't like to walk.

I have a buff Orpington chick that I'm guessing is 2-3 weeks old who doesn't like to stand or walk much. She squats or hunkers down most of the time, and when she does walk, she kind of waddles like a duck. I don't know if this is just a growing phase or something I should be worried about. The Barred Rock that is her big sister (guessing a week or two her senior) doesn't exhibit this tendency, she stands all the time and walks like an adult chicken. Any clues?