Thanks for your question. I'm Alli, the manager of this site.
According to the Harvard health information on our site, migraines should not cause persistently elevated blood pressure readings.
"Migraine headache, or any type of pain for that matter, can cause
your blood pressure or heart rate to go up temporarily. So while severe
high blood pressure can cause headaches, it's much more likely to be
the other way around -- a single elevated blood pressure reading that's
triggered by a headache. Your blood pressure should go back to normal
after the headache resolves.
Migraines should not cause persistently elevated blood pressure
readings. Most doctors won't diagnose hypertension until you have two
or more elevated readings over several weeks. They will also discard
elevated readings that occur while you are anxious, ill, or stressed,
or that are measured within about 30 minutes of a cup of coffee or
It's worthwhile to note one other link between migraines and high
blood pressure: While blood pressure drugs such as beta blockers and
calcium channel blockers may be used to prevent migraines, they don't
work by lowering the blood pressure. Instead, they appear to reduce
spasm in blood vessels that surround the brain. These drugs will help
to prevent migraines equally well in people who do and don't have
underlying high blood pressure."
Also, please feel free to read over the information on MyMigraineConnection.com. I would definitely have your fiance consult a doctor about this-- I hope our information offered some guidance!