ds-mm,
I know how scary this can be. My son Tyler had a stroke on Christmas break when he was 11-years-old. It took the doctors a few months to diagnose what caused his stroke. Once he was daignosed it became scarier because of the risk of another stroke without the surgery. However, I just let the teachers know what was going on and kept in close contact with them. Heck, I got my first cell phone to keep in contac,t with the school. I didn't want Tyler to feel more stress by sitting at home thinking of what might happen, when he could be at school learning and playing with his friends. As a parent I know it is much harder on us than our children. They seem to be able to just keep going and not think about it near as much as we do.
I know many people have migrains with MM, but Tyler had his migrains mainly after his stroke and before his surgery. The teachers would let him sleep at school if the migrain hit him before lunch. Tyler bounces back from a migrain like no one else I have talked to, so this helped him to atleast get a half day in at school if he did have a migrain.
As everyone on here will tell you, every case is different. So, you just need to know how your daughter and her school feels about her being in school during this time.
As far as after surgery, once again every case is different. Tyler had his surgery in June on summer break. He had his in CA and two weeks after the second surgery he was playing in the sprinkler, swimming, and jumping on a trampoline with his cousins of the same age as he was. You can go back through the archives and see how stressed I was, but Tyler just seemed to take it all in stride.
Good Luck my prayers are with you.

Rena