I wonder about that response. Spaying is major abdominal surgery and I think most bithes are not "back to normal" in a short time. In 3-5 days, your bitch should be feeling better, but it takes 6 weeks for a full recovery. Do not allow your just spayed bitch to run and jump, keep her quiet until the vet OK's her to play.
My Beagle was pretty tired for several days. We didn't feed her anything special cause she didn't seem to have much of an appetite, just saw to it that she had water nearby. Our Vet gave Remadyl (spelling?) for 4 days so she didn't seem to have much pain. Just takes time. It took about a month until she was back to her old self.