If the vet didn't give her IV or sub q fluids before sending her home, she could be dehydrated. If you can get her back to the vet easily, I would phone them and ask to bring her in for them to give her fluids. If that is too difficult and she is
alert to take fluids by oral syringe, I would give her some electrolytes that also have sugar in it, like unflavored Pedialyte or even Gatorade. Syringing needs to be done slowly and carefully, and only if the rabbit is alert, or you risk the rabbit aspirating the fluid, which can cause pneumonia. If she isn't alert and is floppy, you need to get her back to the vet immediately.
After anesthesia and surgery, it can sometimes take to the next day for them to start eating again on their own. If it's been 24 hours since your rabbit last ate, then syringe feeding needs to be started. You should be able to get syringe feeding mix from your vet. Common one is Oxbow Critical Care for herbivores. A rabbit shouldn't go more than 24 hours without eating and drinking sufficient amounts. If your vet doesn't have a syringe feeding mix, your rabbits usual pellets can be soaked in warm water and made into a mush to be syringe fed. But you have to use a wide tip feeding syringe or it will clog.
Also after anesthesia, a rabbits body temperature usually drops. And a cold rabbit won't want to eat. So it's important to provide a rabbit safe heating pack for them to help keep warm. I will use a cotton sock filled with rice, heated in the microwave. But you do need to check it to make sure it isn't too hot and can burn them. A hot water bottle can work too, but it will need to be rewarmed more frequently or the cool water will chill the rabbit further.
http://www.bio.miami.edu/hare/opcare.html