She may be grouchy because she is sore and is still waking up from surgery. YY wated to cling to me when she came home - came right out of her carrier swaying and whined to be picked up. Since I had taken the day off to be with her (and I helped in the surgery - I am no vet but I do surgery on humans so I wanted to see how spay surgery would go. I got to help putting her stitches which was neat - even tho I have done it a zillion times on human kids and others, <g>)
Did the vet give her antibiotics? I ask because I recently heard of a cat who died after contracting an illness and her vet did not give antibiotics postop - usually for a week to 10 days. Their immune systems are low and they need the protection.
I would ask the vet for more pain meds. I actually gave my cat some pain meds (I do pediatric pain research so I mixed my own concoction based on what the vet told me about cats and their tolerance for narcotics and what human meds are posion to cats). I hated to see her in any pain!! She actually, as it turned out, needed very little and recoperated just fine!
I hope yours does too but I woudl ask for more pain meds and make sure about the antibiotics.