Good luck on surgery, and stop worrying. I have had over 30 cats get spayed/neutered and most of the time they just became more snuggly. The cats seem to take it in stride, (unlike my hubby who can't take them in for the big day lol), and usually recover quickly.
When you bring her home put her in a familiar place that is quiet and warm, her temp will be off from the anesthesia, and don't worry if she sleeps alot or doesn't want to be picked up. She will be sore for a couple of days and I would make sure that her food/water (when it is allowed) is on the floor so she doesn't have to jump. Put her litter nearby as well so she doesn't have to go too far the first couple of days. If she gets a bump on her stitches let your vet know, most of my latest kittens had this and it was a reaction to the material and considered normal, but I always let my vet know in case they wanted to put them on antibiotics. The bump never turned red or separated so they were fine, but it is a common reaction. My cats never licked or bothered their incisions so I had no need for the e-collar, my vet sent one home with the first kitten in case but agreed to take it back if I didn't use it (save money where u can). Most kittens will be back to their usual ways within 3 or 4 days, most humans will feel better when the kittens fur grows back on their tummies. lol
Oh a couple of tricks for keeping her stress down is to put in her carrier her favorite blanket or one of your t-shirts. My vet is great about putting the blanket or t-shirt in her cage so she wakes up to a familiar smell and this greatly reduces their stress level. My vet also clips their nails for me while they are still under so they can't scratch at the incision. Ask your vet about what time your kitten will be out of surgery and give them a call. Most of the time they will give you an update, it makes the waiting easier. Good luck and let us know how it goes.