Would like to know whether your child had similar cough earlier?
Whether she required nebulisation on and off in the past few years?
Did she have fever with cough?
What I would suggest is to get her examined thoroughly and run few investigation like a blood ,chest x ray and Mantoux test
.If the results come normal then your child could be suffering from allergic bronchitis
or asthma for which she would require bronchodilator
and steroids .So kindly get in touch with a good pediatrician
for thorough examination and investigation.