There are times when the anesthesia used upsets a kitten's system. That is possibly, combined with the pill, the reason behind the kitty's upset.
Another member mentioned adding a small amount of pure pumpkin to the kitten's food. You could also give her a small amount of plain yogurt to help coat her stomach and restore her belly flora or give her a pinch of Asidopholous (a probiotic).
A kitten is so active and on the go it doesn't take much to upset their system. My youngest one spent part of yesterday throwing up because he ate his food way too fast.
I'm sure within a few days kitty will be back to normal. Maybe up till she starts feeling more herself it would be a good idea to add a bit of water to her canned food to ensure she is getting more fluids and does not become dehydrated.
It would also not be a bad idea to talk to your vet's office on Tues when they reopen.