It is best that they are watched for awhile and noon will come quickly.
But for next time, you don't have to leave her at all.
Ellie had a very bad vaccine reaction a couple years ago and now we just hold her in the lobby for awhile. We avoid a hospitalization fee. Ellie is more comfortable. We are happy to be with her. And the vet is in the next room in case there is a problem. We waited for 30 minutes with her last vaccine. Just tkae a book or something.