You can still get her spayed; I am not saying not to get her spayed ; I am just saying that if the vet office told you to fast her for 12 hrs then they are incorrect and that is a red flag...(warning)
if the vet is not on the rabbit saavy list that is another big waving red flag (warning)
I would only go to a vet that is on the list for rabbit-saavy vets or a vet that is recommended by someone who has rabbits spayed/neutered there.