That may be normal, and residual pus trapped maybe in the vagina, which just "washed out". She will be sleepy after her anaesthetic, that's normal too. But I would expect her to come slowly out of that and start to eat. usually the evening after the op. My dog was woozy too for a few hours, but was ready to eat some chicken stew with vegetables I made for her as a nice treat.
But please don't take my word as gospel! I know you may be concerned about "stump pyometra".
If you have any worries at all, about her recovery or any unusual symptoms, do please call the vet back and ask. They are the best ones to advise you.
You could also check her temperature. I would say anything above 102 warrants investigation.
Call your vet back if you are unsure. I don't know if your vet has night duty staff. Ours always did, so it was possible to call with a serious enquiry even if necessary in the night or out of hours.
I hope your dog is doing well after her surgery and will be back to her old self very soon.