Thank you for your query.
is a very non-specific test and does not lead us to anywhere. I would have appreciated if you had shared the values of the total and differential leucocyte count. You should go ahead with the urine examination.
As your niece is eating and playing normally a wait and watch approach would be advisable. In case the above mentioned counts are raised the doctor would prescribe suitable antibiotics.
I hope I have answered your query to your satisfaction.
Wishing your niece an early recovery.