Here is some reading about Mareks disease, but I hope that she doesn’t have that:
https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/poultry/FS-1007%20Recognizing%20and%20Preventing%20Mareks%20Disease%20in%20Small%20Flocks.pdf...
Sorry about your hen. Does she move her legs or feet when you touch them? Does she try to stand and then use her wings to help balance? It may be hard to determine if she has an injury from falling or mating by the big rooster, or if she could be egg bound, or have something like Mareks disease...