How old is she? Maddie was 3 when she was spayed and it took her a few days to be back to herself completely. On the other hand, Cooper who was 1 when she was spayed, was her old self by the time I picked her up from the vet's that afternoon.
You should be given pain medication to help her manage pain and they should ask you to keep her calm a day or so. A good idea would be to make a list of questions and take with you to ask your vet during pre-op or post-op consultation.
Also, she should have pre-op blood work done to ensure there are no problems she may face with being put under anesthesia. I was a nervous wreck with my girls, but they were fine and your girl will be too.
ETA: Pita is a doll and I love her name.