my dog is a boy, so he was neutered, a much less invasive surgery than a spay, however, some things that helped keep him quiet were new chew things such as stuffed hooves, bully sticks, big knuckle bones, etc… he was much more interested in laying quietly and chewing his new treats instead of romping around. also, I was advised to take him out on leash when he went out to go the bathroom, to keep him from running around the yard until he was healed up.
My vet normally keeps all dogs overnight for observation - for spays and neuters. I was a bit shocked when they called me that same evening saying "come get your dog - he's cleared to go home, and making a royal rukus!" I could hear Tucker SCREAMING in the background... the vet's office wasn't used to the basenji noises! hee hee.. tucker was just protesting being in the kennel they had him in, and was missing us. so I went to get him, and he was fine.
don't worry, I'm sure everything will be fine. As long as you have faith in your vet, sandie is comfortable with the vet staff, and you keep her quiet when she comes home, everything should go just fine. It's nervewracking, but it's for the best. so, think positive thoughts, and spoil sandie a little bit more than normal when she comes home.
good luck! let us know how she does.