Katie not eating, withdrawn after fattest

We picked up Katie, our timid little 18-month-old black rescue kitten, from our regular "5 star" cattery on Tuesday, after she stayed five nights over our long weekend. She hasn't been the same since...

- She has barely eaten a thing (she has licked the jelly off some Whiskers chunks and eaten some cooked ham slices out of hand.
- She has been more moany than usual.
- She has been more affectionate than usual, very happy to come over and be petted and even sleep, literally, on us last night; needy.
- She has a real thirst, more than usual, but is making a hash of drinking - getting her nose in it and so sneezing it off.
- She expelled something mostly liquid on the floor overnight but I don't know what it is.
- She had a massive sleep today, from lunch to teatime.

Any advice or theories please??

If things don't look up tomorrow, we're taking her to the vet.

Definitely get her to the vet as soon as you can. When they're not eating they can go downhill fast. Sounds like she may have picked something up from her stay at the cattery (entirely possible no matter the precautions taken), or it could be several other things.