tired of this piece of string

I knew when the Resident Kitteh did not get up for breakfast yesterday that something was off. And today, except for a short trip from the armchair to the bed, she hasn't gotten up at all. Unless she has a remarkable recovery overnight, I am calling the vet in the morning.

She doesn't appear to be limping or to be particularly tender anywhere, although I admit I am only palpating her very gingerly.

She used her litter box once yesterday, but not at all today. She's always been a cat who drinks a fair bit of water but she refused to drink any when I brought some to her, although she did lick some off my fingers. I could hear her stomach grumbling when I was lying next to her, so I brought her a few shreds of cheese which she ate eagerly, but still refused water.

By the end of the day I thought I would try to tempt her with some skim milk, realizing full well that it would probably make her barf. She did not stop drinking for 5 minutes and then she ate a handful of her treats, but puked up the whole works an hour later.

Her skin still feel firm and hydrated but I am getting concerned. And it seems to me that her haunches are a little sunken.

She's still purring though, poor thing.

Do you have any advice?