I've seen banana baby food recommended by others on this forum but I don't understand why and would never give it to my rabbits. For starters, at least in my area, many banana baby foods are 'deserts' and have added sugar. The last thing you want to give a bunny that's not eating is sugar, it encourages the wrong type of bacteria and can make things much worse. Even if it doesn't have added sugar, I still wouldn't give it - banana contains a lot of natural sugar and it's been heavily processed, making the sugars more available. As mentioned earlier, canned pumpkin puree is a safer alternative.
I agree with what the others have said, a post op bunny should have Metacam, even for a neuter IMO as some of them need it and it's better to play it safe. Even my rats all get high doses of Metacam prescribed post neuters/spays and they are not in danger of going into stasis. I don't like the idea of leaving any animal at the vet overnight but all of the exotic vets in my city urge it. I'm on the fence about the practice, I do not leave my animals overnight but I know not everyone recognizes the signs of danger early enough.
I hope the Motrin helps her and she starts eating. She will probably need more fluids tomorrow and Critical Care at this point so if your regular vet is open, you should take her in. It's always a good idea to have a small amount of Critical Care or another syringe feed formula and a syringe on hand in case of an emergency with herbivores. You should be able to get Critical Care from a vet clinic without a prescription.
I hope your bunny feels better soon.