If she is drinking I would worry very much. Although I would contact your vet and let them know. Her tummy is probably still a little upset. Your vet can give you something to sooth her tummy.
Sandy didn't really eat anything for several days after her spay but she was drinking water. She seemed a little depressed and wanted to sleep most of the time. I was told this is perfectly normal, just watch her. Then all of a sudden she was up and going again.