I wish I could tell you if your daughter will grow out of her migraines but everyone is different. I started getting migraines about the same age (hormonaly related) and continue to have them at 37. But they have changed. Unfortunately, mine became worse.
When I was 16 I used to have a visual aura with every migraine and almost always vomited, I only had them a few times a year. Now I've traded the aura and vomiting for daily headaches and dizziness. Again, this is due to horomone changes. So we can't tell how your daughter will change over the years.
As far as the Topamax, it worked pretty well for me but it does have pretty bad side effects. Don't be afraid to let the doctor know right away if she has any bad reactions to it. It's lots of trail and error to find the right medication combination.
If you don't already know, rebound headache is a real concern. If she's taking too much over the counter medication, that may be why she's having these headaches daily. Some people (myself included) believe that the Triptans can cause rebound too - so be careful with them.
There are lots of other infomative websites out there about migraines (do a google search).
I wish you both the best of luck.