Lastly, she probably needs an antibiotic, which you in most cases need to get from a vet, in the USA anyway, if it's an oral antibiotic; but you should be able to get injectible Tylan from a feed store, and if you can, that's something else to pursue. Only saying that because it does sound like a respiratory illness and whether or not it's an infection, an antibiotic might help her combat secondary issues. Normally it's injectible in the breast muscle for three to five days; I know you can give injectible Tylan orally too but there i'm not sure of the dose, but you should be able to find out on here by typing it in the search bar.
I think there's also an antibiotic on line called All in One for birds. I have never bought any, so no idea if you need a scrip for it, but probably. You could check it out though.
In the meantime, try to coax her to eat by offering bread crumbs soaked in buttermilk, or scrambled eggs, yogurt, finely chopped grapes, applesauce mixed with crumbles, anything she likes that has some fluid in it too. You can gently dribble fluids into the side of her beak, with a dropper, making sure she swallows..a little at a time.