my kitten did the same thing when i took her for the first vaccination few weeks ago, i was worried too! she just slept nearly all the way through for 24 hrs or so, getting up to play for literally 5 mins every now and then, and didn't eat either, but by the day after she was back as playful as before! she's getting the 2nd one today, hopefully it wont be as bad.. i was feeling so sorry for her!
lots of cuddle to your baby, im sure she'll be fine soon!