I read your question carefully and I understand your concern. If she hasn t a history of previous headache I think that your daughter should be carefully evaluated. The early period after birth is a period of higher risk of complications due to enhanced blood clotting, such as cerebral venous thrombosis which can manifest with strong headache. So she should be evaluated by a neurologist and preferably have brain imaging with contrast CT or MRI. If those result normal then there are several pain killers, treatment usually consists in non steroidal antiinflammatory drugs, triptans, opioids. I hope to have been of help.