I would track it. Be meticulous for a few weeks if you can handle that. Track her eating, activities, her period, any headaches and stress stuff. It might give you clues all in itself, otherwise a DR might ask you to do something similar. This is what I was asked to do before getting further medical intervention. They wanted to know what I ate and drank, how active I was, how stressful my day was, etc.
The other suggestions people had are spot on too. Limit stimulant foods/drinks, get plenty of activity in earlier in the day and a generous calming end to the day (a big issue for me personally is shutting my brain down..."to do" lists and all the upcoming weeks things just flurry thru my brain and I can not make it go away). Mindless TV (stuff I have seen, etc), or reading helps. Currently I actually sleep with my MP3 player and headphones in...so there are NO noises but the music I choose...usually mellow like Jack Johnson stuff...and that helps me a TON to block out all those other noises I obsess about.
I have suffered from insomnia (along with migraines unfortunately) since I was a preteen and hormones kicked in. I am now in my early 40's and have to take medication to sleep. I just can NOT do it otherwise. I can't fall asleep and I can't stay asleep. My brain is just wired goofy. I keep hoping menopause will change things for me...