I work on a petting farm that has every conceivable farm animal, including chickens. It's possible she's broken her leg. The good news is, they often heal very well on their own. Splinting is sometimes an option, but not always. As long as the toes on that foot feel as warm as the toes on the good foot, you know she has circulation there and that's a very positive sign. If it starts to feel cooler than the other one, then a visit from the vet is in order.
Keeping her separated for a few days is a good idea. But her pen should be large enough to allow her to move around a bit, not confine her to the point of only being able to lie down.
Good luck and let us know how it goes.