Ok, can you bring her inside where it's warm? You will need to examine her and look for other signs & symptoms. Is she having any respiratory problems? Sinus drainage, wheezing, swelling in the face and eyes? Check her vent area to see if she is egg bound. Is she bleeding anywhere, or have any wounds? How old is she? Look for signs of lice or mites? How does her poop look? Is there any blood in her poop? Is she limping when she walks? Check her crop to see if it's empty or full. Is is hard or squishy? The more information you can give us, the better.
Also, do you have any poultry vitamins and electrolytes you can mix with her water. You may have to gently dip her beak in it, to encourage drinking. If you don't have any, you can use Gatorade mixed with water. 50/50