I second the idea of dehydration as a factor that can push one towards migraines. My
experience is with cluster headaches, a neurovascular headache that is similar to migraine in terms of therapies that work, although the symptoms are rather different. Some people benefit from the W3 treatment - Water, Water, Water ... for an average person, that might involve one 8 or 12 ounce glass of water every hour on the hour for 8 - 10 hours a day.
Kudzu root is another alternative to consider. Kudzu has a unique isoflavone that tweaks the serotonin in a rather specific way, blocking the 5HT-2C receptors. It has been used for headaches in Chinese medicine, and a few years back, was the topic of interest on a cluster headache message board ... I posted the research, a regular poster from Arizona tried it, and after being chronic (daily cluster headaches for over a year) she went into remission. There was a
thread where people reported their results, and roughly 70% of the people who posted (most of whom had long standing issues and had tried everything) reported good or excellent results. Needs to be taken regularly, as it is a temporary shield ... people were taking 2 or 3 doses a day, and if they skipped a dose or two, the symptoms returned. So not a miracle cure by any means, but if it provides relief, that can be valuable to people who are really suffering.
Oxygen is another treatment that helps most clusterheads - not the trickle one gets from a nose clip, but a high flow stream of 100% oxygen (12-15 liters per minute) from a non-rebreathing mask. This has been validated as a prescription treatment for cluster headaches, and the reports are that spouses with migraines have also found benefit from it.
A third option worth considering is curcumin, from turmeric.
If someone is on another medicine, need to consider interactions. For example, if they take triptans (imitrex, etc) then anything that affects serotonin could cause problems like serotonin syndrome - even if the second medicine is 'natural', the combination is not.