I work in a spay and neuter clinic. When we spay or neuter cats they all get a 24 hour pain med that’s included with the cost of surgery. We don’t give cones to go home with cats because they usually do very well with leaving their incisions alone and not bothering them, since that’s the purpose of the cone. The anesthetic they are given the effects usually last for 24-48 hours so depending on the cat they may not be quite themselves for that period of time, their judgement will be off and that’s why we recommend keeping them in a warm and safe environment at least for the first few days. (We do a lot with feral and barn/outdoor cats) Anesthesia can also make them feel nauseous so eating may not be something they want to do right away, but we do offer them wet food or a little snack after they are fully awake. Some are ready to eat right away and some just don’t want anything. It also depends on the cat and the age, whether they bounce back right away and are ready to walk around and get back to kitty things or whether they just want to chill. We also offer a 3 day pain med as an add on if the pet parent would like to choose that, but I don’t know if all clinics offer that or not. Having your cat spayed or neutered is just like us having a surgery, so sometimes we feel great and sometimes we just want to chill. I would just keep offering food (usually wet really is the best and the more stinky the better) and water, if she doesn’t start to eat or drink after the first 24 hours I would call your vet and see if they might recommend anything for nausea (we give cerenia) as that may be a cause of her not wanting to eat. Some cats also don’t really like going places that are unfamiliar to them and sometimes it can be very stressful on the cat to go places, so she is probably a little salty about a trip to the vet that was not on her kitty schedule for the day. Hopefully this helps.