You should call your vet. She should have eaten something by now, at least had a nibble on a treat. Call your vet, it’s been too long since she ate, maybe they’ll want to give her gut motility drugs and maybe warmed-up replacement fluids. She should absolutely have pain meds. She was probably given a shot that still has effect, but after a spay a girl bun should have pain meds for 5-7 days.
You must syringe feed her if she’s not eating. You can soak pellets in water and make a mush. You can add some grated apple or a tiny amount of mashed banana to help perk her up. Sometimes they start eating if they get something in them.
I would however call the vet first of all. If her ears feel cold at the touch and she’s not moving around, you could give her a warm water bottle wrapped in a towel to help get her body temp up. Make sure she can move away from the heat source if she doesn’t want it.