Viruses such as infectious bronchitis and others will usually run their course over weeks of time, the way humans handle colds and flu virus. They can be infectious to others for a few months. You may see others getting the symptoms, but eventually it will go away.
Does she have any nasal drainage, bubbles or foam in one eye, or any swelling around an eye or the face? How often does she sneeze? Have you added any new birds recently? Does she sound at all like the silkie in this video with stridor: