How long has it been since you took her in for the spay and when she last ate? A rabbit shouldn't go more than 24 hours without eating a sufficient amount, though even at 12 hours I start to intervene. If it's been 24 hours you need to call your vet as you will need a syringe feeding mix and instructions on feeding as your rabbit will need to be syringe fed until she starts eating on her own.
For my rabbits that had the hardest time getting back to eating after their surgery, I had the best luck getting them eating by offering leafy greens like cilantro, parsley, carrot tops, dark leafy lettuces. One rabbit would only eat a little bit each time so I gave him as much wetted greens as he would eat, every half hour for about 36 hours, then he gradually started to eat more normally after that.
A few things about post surgical care, a rabbit won't recover well or want to eat if they are hypothermic, so it's important to monitor their temperature and if chilled, take active measures to keep them warm. With mine I would regularly check their ears as that gives a good indication of body temp. If they felt cool at all I would provide some sort of rabbit safe heat source, like a snugglesafe or warm pack, and make sure they were warming up by or on it. It's also important that they have a take home pain med, preferably meloxicam, that is dosed at the higher range to help control pain. I don't like the narcotic ones because they tend to be given at a dose that causes lethargy and the gut to further slow down.
https://rabbit.org/post-surgical-af...s to begin,24 hours consult your veterinarian.
http://www.bio.miami.edu/hare/opcare.html#neuter
