There is also a group of migraine sufferers who get migraines (as I used to) linked to their monthly cycle, when hormone levels change. I used to have dreadful migraines each month. Your wife needs to see her GP, to determine what can be done.
I found that taking two stemetil (prochlorperizine) when symptoms began, plus paracetamol and codeine 4-hourly, helped - but tbh it's often a thing she has to live through until it clears, it's a vile condition.
Stress certainly doesn't help but mine also reacted to red wine, chocolate, onions, and oranges - I avoided those items.