Welcome to HCM,
It seems that she might be having allergic cough
giving rise to this problem.
But as she is not responding with anti allergic medicine, there might be having some other problem as well.
Among children Eosinophilia
is a common condition where cough does not respond to common medicine.
At this age worm infestation is common and this causes Eosinophilia.
Go for blood and stool testing and if there is Eosinophilia, a simple course of Di ethyl Carbamazine will solve her problem.
You can give adult Nyquil
but half the dose.
Avoid fried, cold
drinks and junk food.
Ok and bye.