She sounds like she has a respiratory infection. Keep her isolated from other birds, and give electrolytes and probiotics, and keep her warm. See if this helps.
The disease could be bacterial, in which case you might want to get antibiotics. Antibiotics will not treat a viral respiratory disease, only a bacterial one. Tylan50 is one of the best respiratory treatments. The dosage is 1cc for large fowl, .5ccs for bantams, injected into the breast muscle once daily for 5 days. Alternate the side of the breast that you inject into, as Tylan can make the injection area sore. During Tylan treatment, do not give probiotics or dairy products.