Thanks for writing your query.
Your granddaughter seems to be suffering from upper respiratory tract
The causative organism can be viral or bacterial. Clinical examination is necessary for proper management.
You should get following investigations done :-
1. Throat swab culture.
2. Complete Blood Count(CBC).
Treatment can be planned according to the reports of the investigations.
You can give antihistaminic like cetrizine
, after discussing with her Paeditrician, for relief from dry cough
I hope this is helpful to you.