B.C.
A few years back I had a cough that would not go away for something like 12 weeks.
Nothing helped.
I began drinking some echinacea tea and it cleared up in about 2 weeks.
I have no idea if the tea worked or if the cough finally quit on it's own.
I thought I might have walking pneumonia but my Dr said it was just one stubborn cough.
I never had a fever and I never took any antibiotic for it.
You could try having her use a neti pot to rinse her nose out with warm saline.
Does she still have her tonsils and adenoids?
Maybe you should take her to an ENT (Ear Nose Throat) Dr and see what they say about it.