O.K... this is a little convoluted... it is, these are excerpts from e-mail.... back and forth.. when dawg53 helped me through this same thing and I was so "freaked out" and scared....... So.. check this out and also search this website for "relevant" respiratory disease threads...
O.K.... Did you just get her? Did she get sick about two weeks after you got her or introduced new chickens to your flock?
O.K... Look for posts by dawg53 regarding Denegard, Oxine, and CRD or MG..... You need to treat this strongly, thoroughly, immediately...
I'm "rusty" on this...