Thanks for query,
First of all we should find out the cause of her coughing.
I suggest for,
1, CBC and ESR.-to rule out infection,Eosinophilia
2,chest X ray
3, stool test
to rule out worm infestation,
4, Try to find out any allergen causing this coughing like atmospheric allergen,cosmetic or food allergy
After all reports we might have some clue regarding her problem and then go for the treatment accordingly.
Ok and bye.