Does your bird have a really bad odor? if not, it could be CRD. Read the blue link below on my home page. Its a issue that we all have, referred to as Mycoplasma's a chronic bacteria passed down through the egg (transovarian) and so on. Place bird in a safe place where she can get fresh air, quiet time and only treat with an antibiotic if it becomes a secondary infection.
Let her work through this on her own or you can have blood testing done through your State Veterinarian or the county Extension service can direct you to your states diagnostic lab.
Good luck!