Dear Tammy,
It is absolutely normal for her to be groggy. Very deep anesthesia is used as a spay is major abdominal surgery.
Keep her in a carrier until she is more alert so she does not injure herself. Do not try to feed her until she wakes up suffiently because she can choke if her swallowing reflex is impared.
Do not give her any human OTC's for pain because most are toxic to cats.
If she looks to pull the stiches, you can cut a sleeve off an old blouse or sweater and use it like a tube top.
Just keep her as quiet as possible tonight and she should be fine.
See your own vet first thing tomorrow. Coming from a shelter, she should be on antibiotics so she does not develope an infection or upper respiratory virus.
Please let me know if you have any more questions. I will be happy to help in any way possible.
Warmest best wishes,
Terri
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