I agree, if she's indicating that the joint or leg is tender when applying the gel, I would lean toward a sprain/injury as well.
I too leave mine to move about with their flock and interact, even with injuries or when sick/not well, as long as everyone is agreeable no one is picking on them. I think it's good for them to just be with their flock even if they aren't moving about a lot.
If it's really cold, you can provide her with extra bedding since she is currently sleeping in the shavings. I had a hen with a fractured leg. I left her with her flock. She was splinted and wrapped, she was still able to get to food/water fine, no one picked at her and for weeks she slept in a wood box on the floor, then graduated to a low roost, then finally as she healed and tested her limits, she eventually began roosting in the rafters again. Chickens are pretty good about self-limiting activity, sort of like we are, if it hurts, rest it and see if it improves over time.
If she were mine, I'd still finish the Calcium out to a full 5 days, just to be sure the limping is not due to the need of expelling any egg material, etc., but with tenderness, she's probably sprained it.