First of all let me tell you that a given medical problem can be due to various cause and the basic objective of the attending doctor is to establish the cause and treat accordingly. Back to your problem, your daughter has two problems probably, one is migraines and the other could be narcolepsy
as per your doctor. Headache can be due to various cause like brain infection, tumor, migrains, problems in the blood vessel in the brain etc. If these causes are excluded than the possibility of primary headache syndrome
is entertained. Migrain can be treated with topiramate
(not a good option in girls), propranolol
, amitriptiline etc. Coming back to the second part, only sudden onset and short latency to REM sleep may not suggest narcolepsy.These can be modified by medicines too. You have not mentioned the sleep medicines that she is using. You can observe if she is completely asymptomatic as of now.
Hope this clarifies