Cat kibbles are an excellent supplement, dog food not so much. I mix scratch, cat kibbles, and pigeon seed or wild bird seed. The chickens love it when I toss out a few handfuls of this mix.
You can probably speed her feather growth with Feather Fixer or other vitamin/mineral supplements. My understanding is growing those feathers requires certain cheleted minerals and the regrowth can be sped up by providing them. A good normal feed has these minerals at the normal levels, but not...