I tried finding a BYC article on slings, but I didn't have much luck on that. I've had plenty of leg problems with my Cornish Xes, but because they was food, if a leg problem came up, for them, it was over. In your latest picture, it looks the leg is swollen. How old is she? I don't think that she's a Leghorn. How the RIR is so small next to her, I'd say she's Jersey Giant?