Poor little sweetie. Does she seem to miss her flock? She might enjoy some visits with them inside a dog crate when the temps are better, or by bringing in a friendly mate to visit her inside. Please let us know how she gets along. If a vet and xray is possible, it might rule out a leg or hip injury. But those can be pricey. Here is a link about homemade chicken sling chairs that you can make for disabled chickens to get them up and in front of food and water (design is in post 11
https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/

https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/