Sometimes when one of my birds is stressed they like to eat baby food (chick starter) for a few days...I offer them free choice of their regular food and starter -- Birds aren't people, but they sure can react to stress...I had one little hen die grieving over her little friend hen's death. They were best friends, together all the time. The little one crawled up under a group of birds when it started turning cold and got smothered. The remaining one started drooping more each day, quit eating -- and finally just gave up. So, maybe it's just stress from the fighting roos and your little hen will be fine in a few days. Warm is definitely good, dark is definitely good, special food is definitely good -- but if you stay up all night trying to get her to eat, you won't have the energy to deal with them tomorrow.