My new cat doesnt seem to be eating/drinking properly?

She is 3 years old, been desexed, and we got her from the local animal shelter four days ago.
They told us there that she has dry food and water available to her all day, and they give her canned food (Whiskas) twice a day. She has been eating dry food without a fear, but in the whole time she's been here she has only been for water once and never even touched the canned food. She smells it but just won't eat it. I am getting worried that she isn't hydrated enough Might I add that shes only been to the toilet in her litterbox once the whole time shes been here.
What can I do?

At 3 years old it will probably take her some time to settle in, you could get some Rescue Remedy from the chemist (around $20 in the vitamin section) and either squirt it right into her mouth or pat/rub a few drops onto her head/outside ears - this will help her feel calm and relaxed.

Are you sure she's not either drinking when you don't see, or perhaps licking the shower etc. after use?

And she may be toileting elsewhere.

Just try her on a few different types of canned food - maybe she doesn't like Whiskas or is used to another type or flavor. Cats are ridiculously fussy about food, and need constant changes so as not to get bored.