Need Advice - My chicken hurt her leg

I have a chicken who is about 18 months old and she will not put any weight on one of her legs. She was totally fine, running around the yard and when I went to close the coop door the other night, she was sitting on the floor of the coop. I went and picked her up and she would not put any weight on her right leg.
I checked her foot and leg for any obvious sign of injury and could not find anything. Her foot looks fine and she will curl her toes around my finger without any trouble. I cannot feel any broken bones or anything out of joint. She does not make any fuss with me poking around on her leg and her leg and foot feel the same temperature as the other one.
She is eating, drinking, pooping and laying like normal.
She has been this way now for almost a full 7 days without any improvement.
Does anyone have any ideas on what I can do for her? The other chickens are not bothering her so I have not separated her from the flock. Any advice would be appreciated. I feel so bad for her.
Thank you!!

More than likely, she has suffered a sprain. Swelling or bruising could indicate a broken bone. Forcing her to rest her leg in a crate for a week or two with her own food and water would be a good way of forcing her to rest it. Make sure that she is eating and drinking normally, and vitamins in her water would be helpful.