Does she have any discharge from the eyes, nares or beak, or any plaques or lesions inside the beak/throat? Any bad smell around the beak or head, or swelling around the eyes? All of those are common respiratory symptoms. It also could be stridor, which is a partial blockage of the airway, often from a bit of feed that gets stuck. In that case it usually resolves on it's own with some time. You can look in the beak as far back as you can see to see if there is anything obvious. Stridor can also happen from swelling or mucous with a respiratory virus. There are videos of chickens with stridor if you search for them, to compare.