Welcome to Healthcare Magic
Firstly show your daughter to an Ophthaomologist at a Hospital. Maybe there is some problem in the eyes like high pressure which is causing pain. If the Ophthalmologist says her eyes are not the cause of the headache then she needs to see a Neurologist
to rule out Migraine
which is severe one sided headache with vomiting
and seeing lights and colours, or any brain masses which is causing pain. How old is your daughter. She can take a pain killer over food under medical supervision for the headache in the time being.