Hi Cookiebun,
That a female is not moving 24hrs after her spay is not alarming, it’s a pretty invasive surgery so she’ll just want to be calm and quiet (like us!)
The fact that the emergency vet said she is prob in GI stasis and didn’t give mover meds is more alarming (or did they? this is not the same as pain meds).
If she is eating hay and treats then give her those, no problem. The rules for treats go out the window for 24 hrs, to get her eating again offer anything (within reason!! lol).
Her temp will have dropped probably so it is vital she is kept warm (hot water bottle, hand warmer wrapped around tshirt or something, fleece over her) make sure she can get away from the warmth if she wants to.
Hand feed her treats so she is interested in it.
It is important that she poops and wees. Her poops may be squishy and funny shaped for a while (couple of weeks), but as long as she is eating and pooping, she’ll be fine.
If she is still NOT eating – you will have to syringe feed her Critical Care, or mash up some pellets or pellet dust so it goes through the syringe ‘hole’.
I’m sure you absolutely know the importance of a bunny eating. If he/she doesn’t, he/she is at high risk of dying because the digestion process slows down and stops.
A rabbit savvy vet would never advise to fast a bunny for 12 hours – for whatever reason.
If in doubt, go back to the vets. Better to be safe than sorry. 