Migraines are usually the symptom of some other cause and a trip to the doctor is probably the best idea. However, magnesium rich foods have been proven to reduce the symptoms and frequency of migraines.
Try mixing half a teaspoon of cinnamon with one teaspoon of pure honey. Doing this once a day for children has proven very successful. Cinnamon is high in magnesium and is a natural anticoagulant that will help return the blood flow to normal levels. This also won't interact with any medicines or pain killers that your daughter is taking as it is natural.
Can't guarantee success but it's worth a try.