I absolutely would not leave her overnight unless staff is also going to be there overnight to monitor her. I heard a horror story of someone who left their dog overnight after a spay, and the dog was by itself all night. Ended up having a complication and died b/c no one was there. If the dog would have been at home the owner would have recognized that something was wrong and would have been able to take the dog to an e-vet and she would have been fine.
Years ago when my mom had her two labs spayed, they did not stay overnight. I don't know if overnight stays are common.