Thank you for your query,
syrup is used for cough associated with wheezing
and it is not indicated in cold.
For cold you can give oral antihistamine like chlorpheniramine
in prescribed dose.
For immunity give balanced diet, immunize her appropriately for her age.
Recurrent cough may be due to some allergy or underlying hyper reactive airway problems.
Avoid exposure to cold air, dust, pollution, and to pet animals and known allergens.
Hope I have answered your query.