Since you say she has been sick for the past 5 days and her oral intake and activity is also low, its better to have her investigated. Basic blood investigations like Complete blood count
, CRP with X ray
chest will be helpful.
Antibiotic may take 48 hrs for acting. Its not clear how long has she been on antibiotic.
Based on chest x ray, a change of antibiotic may be needed.
Give her food of her choice with plenty of fluids.
Hope my answer helps you.
Wish a speedy recovery for your daughter.