hello.please see your daughter is examine and eveluated by a good physician.
if she has persistent cough, she needs to be investigated thoruoghly.also look for the additional symptoms like weight loss
(blood in sputum), persistent low grade fever
looking at her history she definitely requires an X-ray examination as there is list of conditions diagnosed on X-ray which can give chronic cough
.the test should also include sputum examination if she has productive cough a long with the basic blood tests like an ESR
, total blood count, differential count etc to look for infection.
there is no inhaler for viral infection.
cancer is rare at her age if she is young and there are other additional easily curable causes to be ruled out and then think of cancer.
so a good qualified physician is what you need.
hope i have helped you.