I did have a couple of friends who were older than that and still wet the bed, one of them regularly. The only way I can suggest is that you help her pick out some sheets for her hotel room bed, a couple of bottom sheets, and tell her you will wash the sheets every morning if you have to. I'm not sure about CR, but at the Values the laundry rooms are next to all of the pools. It would take less time than eating your breakfast.
My daughter's first trip was when she had just turned 8, and it's such a magical time because they are still princesses. We did BBB of course and all of the princesses made a big fuss of her when she was in MK sporting her new princess dress and sash....we did the works including the photo shoot. Disney doesn't provide anything special for birthdays but you can arrange to have something delivered to the room like flowers or a balloon bouquet. If you opt for a value or mod resort you can decorate the room window too.
I have done the long drive...for us it's 32 hours. It's 17 just to get to our family Ontario. It's not horrible if you have no other choice. We would do that in 2 days. We camp along the way in summer but we book with
Hotels.com wherever we are when we have to stop for the night. There are lots of tips about driving down on the Transportation Board. Having said that, you should look into things that can help you get over your fear of flying...it is possible. I totally understand because I was in a plane that had turbulence and wind shear and it wrecked me for a while, but you just need to get through a few hours and I'm sure some day you'll be able to do it.
I've been to every resort and I understand your wanting to stay at the CR, but if you haven't looked into the other resorts you should. When my daughter was younger her favourite was the Ariel section at AoA, but for a first trip and being so young she will love any resort. I second the opinion that you're going to need to buy lightning lanes to get through the crowds...if that's going to make your trip too expensive then you should look into other resorts.
A big yes for naps from us...in the middle of a park day or a dance competition.