Mycoplasma was my thought, which is why I asked if it was her face that is puffed up and if the noise was her breathing. If so antibiotics is the only sensible option and you'll have to take her to the vets for that as it's not something you can get on-line. Some birds have a natural immunity, but it is infectious and will spread to the other birds. It's not necessarily fatal, particularly if treated, but they remain carriers, which has implications with regard to any new introductions to the flock. She will keep eating and drinking, she may even recover on her own, but as you have other birds I would play safe, go to the vets and get treatment for the whole flock. Not trying to scare you, but it's better safe than sorry.