Ditto.......syringe feed if all food is refused. Vet should have OTC liquid hi calorie supplement for nursing or recuperating pets. Try the smelliest fish based wet food, tuna and sardines might work, too. Remember this is a total hysterectomy and it's gonna take time to heal. I've had some that took almost a month before returning to their energetic pre surgery selves, she won't be healed completely on the inside for 2 to 3 months. Pet stores and farm suppliers will have the supplements also in liquid, paste or gels. Small amounts fed frequently should help.
Not a vet, but as a retired vet tech/rescuer have been thru this many times.
best wishes
I would try a different vet! If your cat isn't eating she will not make it thru whatever it is that is affecting her. You need to move fast, if she hasn't eaten for a week her liver is going to start failing. I would keep up the syringe feedings, they might be stressful to her but they just might save her life. There are several videos out there that can show you easier ways of doing it. Good luck!