I think different brands have different amounts of protein in their grain. Giving her scrambled eggs and/or plain hamburg is another way to give her more protein for feather growth.
Chickens typically don't hurt themselves to that point unless something is wrong. I would question if others were doing this to her. With pinfeathers, you want to avoid touching them as much as possible. If others are pecking at them, I would separate her in a crate that's in with the others (so...