I know it is very difficult to not worry but she will do fine. I have had 3 or more Labs spayed over the years. My dogs haven't had any negative effects from the surgery. The vet will make sure she is safe and comfortable and I know my vet's office has vet techs come in during the evening to check on the patients.

She will probably be a little sleepy when you bring her home. Just make sure you don't feed her or give her too much water right away when you bring her home or she may get sick. They will tell you to keep her calm and quiet for a day or so.