Awww poor little love. Personally I would not syringe feed her tonight - she has had major surgery and is bound to feel poorly and stressed, that's quite normal. I would be inclined to leave her somewhere warm (you can do her a bottle but make sure she has enough space to get away from it if she gets too warm; it's not cold at the moment so she should be fine just in a normal room indoors), quiet and dimly lit, surrounded by some tasty treats and a bowl of water, and just leave her to settle. By jumping in too quickly with syringe feeding I think you can do more harm than good with a new wound and adding extra stress, which can make the cycle self-perpetuating at this stage. If she's drinking then that's brilliant as that will help to flush the anaesthetic out and keep her gut contents hydrated.
If she isn't eating tomorrow, however, I would definitely go back to the vets and hopefully they will give you more pain relief and a gut stimulant.