First of all I don't want to alarm you, but will your kitten be having tests to ensure she is fit enough for anaesthesia? I always have ours checked before they have to "go under" as one of my "girls" had a bad reaction to the anaesthetic when she was spayed and it was touch and go for a little while. We'd no problems with our other cats. Just keep an eye on her when she comes back and if she is very listless and floppy, take a look at her gums and if they are a very very pale pink get her back to your vet pronto. I wanted to alert you to one possibility, I'm sure everything will be fine and she'll do well.
I'm happy to say my cat recovered well and is curled up on the sofa beside me