When should i take a child to a dr over a cough? she has a cough for week and half and no sinus issues

Cough in children: is usually caused either by a viral illness or allergies. If the child is acting normally, eating and drinking well, and does not seem to have trouble breathing, the cough should pass on its own, although it can last 2-3 weeks. If she develops high fevers, uncontrollable vomiting, or is not acting right, it is time to see a doctor. Hope this helps!