Nala just got spayed a few weeks ago and I was just as nervous as you! We picked her up and the vet had already given her meds to get her through the night and pain meds for us to give starting the next morning. She was very groggy for the first couple of hours but then was starting to get back to her normal self....just slightly less so. She slept in her crate on our bed so we could check on her. By 24 hours later she was FINE! We had a baby onesie on her to keep her from biting her stitches, and never really touched her scar (the vet used a laser so it looked great right away). Don't worry....she'll be herself sooner than you think! She was my second puppy and I was still a nervous wreck...I called the vet 2 or 3 times that day checking on her
Make sure you give her the pain meds the first few days and then depending on how she is doing you can decide if she still needs them or not. We had a week-long supply but only used about 4 or 5 days worth, and the last day was partially to make her sleepy for the car ride from: NY to MD so she wouldn't bounce up and down and tear her stitches.
If the scar is hot to the touch or red and very painful, I would call your vet to check to see if she thinks you should bring her in.