It is hard to know whether it is viral or bacterial, or even from mold fungus. Symptoms sometimes can make it more obvious to tell one from the other. Normally, I would not treat with an antibiotic for mild symptoms, but she seems to be in distress. Is there any way that you could take her to a vet? I hope that you see some improvement with the doxycycline. I would try to get her eating and drinking. It won’t hurt to worm her as well. While you are handling her, it might help to look into her beak and throat for any mucus or yellow/white material.