I don't know what actually triggers my migraines however, I do know just prior to it becoming a full blown migraine.
I had one today in fact. I begin to see these zig zags in front of my eyes and they slowly grow and undulate until I can't see.
I wasn't able to see the computer screen at one point and didn't fully realize it was that early migraine symptom.
If I catch it while I'm still just having vision disturbances, I can, 99.99 % of the time, knock it out with a nice double dose or two of Advil and a caffeine drink (it's believed the caffeine helps the Advil to work faster and it seems to work very well for me).
It works quite quickly and usually within 30 minutes it will be obvious that I'm not having the blind spots in my vision anymore and it never develops beyond that point.
If I don't catch it while in that early stage, the game is over and I'm out for about 24 hours with the usual severe head pain and vomiting.
Good luck to your friend. Perhaps he/she isn't really believing that the meds can help. ??? I can't imagine not trying because they are SO miserable.