Hi J.. I just wanted to second the suggestion to move off the narcotic pain relievers. Children do really well on plain old tylenol once you are past the first 24 hours after surgery. My son had major surgery last spring involving his hip and mouth. He does not have a high tolerance for pain but once we made it past 24 hours, he preferred plain tylenol. After 2-3 days, he didn't take anything. The narcotics will upset her stomach, suppress appetite and can also cause constipation. It is worth the side effects but you want to stop them as quickly as possible.
Also, keep a close eye on how often she goes potty and how long before she has a bowel movement. If she is not going pee, then she is dehydrated and needs to be seen right away.
One last thing, when my son was five, he had another major surgery---a very hard one. He refused for several days to take anything by mouth. Normally, I would not worry about discipline issues at a traumatic time such as this (particular where there can be fear involved) but after several days in the hospital (and knowing we couldn't go home until he started drinking), we insisted that he drink something before he was allowed to play video games or watch tv. I *hated* to do that but he *had* to drink. He was afraid to drink because his throat hurt. No amount of talking would convince him that drinking might actually soothe his throat. Once we insisted, he saw for himself that drinking helped. We let him choose whatever he wanted (which ended up being hot cocoa) and once he started drinking we praised and made a big fuss. good luck.. . I hope she starts drinking soon. If you need any ideas fora liquid diet (if that is required), I have a huge file I can send to you if you send me a private message with your email addres.. good luck