Your sister took DOTS that means she has recovered completely from tuberculosis
,It is possible to have allergic reaction
and to develop hypersensitive lungs just like asthma
if she gets breathing difficulty also along with cough and cold.
Kindly get PFT(Lung Function Test) and Allergy
test if required.
Anti allergy treatment she is already taking. This would be unethical to advise any medicines without proper examination. This not a forum to get prescription.
Please consult your treating physician