New cat still hiding after 30 hours

I would not say I am worried, but just wondering how long this might
go on and how I might coax new cat Destiny out of hiding:

Picked my new 1 1/2 year cat
up yeterday from the cat room at the Humane Society where
she seemed fond enough of my petting. Took her for a vet exam
and shots on the way home. SInce coming home, she's spent
almost all the time out of reach under the queen bed, avoiding
Duey my 10 year old cat and me. Not making any noise, except
some pleasant sounds when I reach in and pet her. She also does
not appear to have drank, pooped or peed in that time. I did put
her in the bathroom overnight (after dragging her gently out from
under the bed without any apparent fuss on her part), with food and
water, but she crawled up in the linen closet and ate neither.
I did this so she would not have an accident but left the bathroom
door open. SHe never left. She did nibble a few pellets off
the floor when I took them out in front of her.

Bottom line, I suppose this is fairly normal (?), but can anyone give
me a time frame after which it's not? SHe ought to be getting
pretty hungry and thirsty. She's not listless,

TIA