I own a macaw rescue here in N. California and these are the number one most 'allergen sensitive' bird among psittacines. The question is what can your daughter do to help her companion breathe easier. Thank you for not asking for a diagnosis. Your daughter is already doing all the right things there. Veterinary intervention is the only way to know for sure what the long term treatment is.
For right now I can give you what I do for the macaws that become congested: If your bird is perching, cover the cage on all sides and top, leaving only the front uncovered. Place a regular vaporizer without anything in it on the floor in front of the cage. The warm, misted air and enclosed area can often be soothing. Be care to not aim the vaporizer right into the cage or even put it on the same level - you don't want to impair the breathing or overheat the bird
If the bird starts to lose the ability to perch or seems more distressed, you might want to make a brooder box
For a makeshift brooder, use a small box lined with soft clothes like tee shirts.
Use a thick, clean sock and fill it ¾ with plain, raw white rice. Knot the end and microwave it for about 1 ½ minutes. Shake it afterwards to distribute the heat and be sure it's not too hot. Tuck this in just under the cloths.
A heating pad under one half of the box is also helpful, set on low. This is one of the few times I’d ever use both heat sources if necessary to maintain incubation temp (90-105 degrees).
If ever using an electric source for heating anything in anyway, please be vigilant and constantly double checking carefully.
Gently drape a light cover over this box to further help hold heat in and keep light low.
Seeing her vet on an urgent care basis may also be necessary -- the vet will have options we cannot duplicate at home.
Let me know how it goes ok? My computer is terribly sluggish right now so I'm signing off for the night. I'll be back tomorrow a.m. ok?