Welcome To BYC @rckehllrchicks
How is your hen doing?
How old is she?
What are her symptoms- coughing, sneezing, wheezing, mucous from nostrils, watery eyes, swollen face, bad odor about her, etc.?
Do you have vet care available?
If she is unable to drink or eat on her own, you need to try to syringe or tube fluids into her. Dehydration comes quickly. Once she is properly hydrated, offer wet poultry feed, hardboiled egg or tuna and see if she will eat.
If she has Infectious Coryza along with symptoms of facial swelling, heavy smelly mucous/discharge from the eyes and nostrils, then you may need to treat with antibiotics to help with secondary infections. If you have a vet that can give your meds, that would be best. You can try injectable Tylan50 which can still be purchased OTC at most feed stores, but your vet would have something better.
Keep us posted.
https://www.backyardchickens.com/t/805728/go-team-tube-feeding starts at 15
http://lafeber.com/vet/tube-feeding-birds/
http://edis.ifas.ufl.edu/ps044