Adopted cat doesn't want to play
TLDR: I took in a two year old cat in September. She keeps sucking on her paws for comfort, afraid of basically anything, eats only dry kibble, extremely shy, bites when being pet and barely plays. What should I do?
Kami, the cat in question, was surrendered to me because she was terrorizing an old and sick feline roommate and their owner could not bother doing anything about it other than getting rid of the cat.
She is physically healthy, tests didn't show anything, doctors said she is fine, but after a very long and tough period of adaptation she remains very nervous, shy and rarely asks for attention. I know that Kami has been picked up from the street and separated from her mom at the age of two months and that for two years she had only one toy and no scratching pole, which tells me she was probably not interacted with a lot and mostly ignored.
I want her to eat wet food to avoid kidney stones, correct mildly annoying behavior of asking for my attention during work time and night and, well, be able to pet and cuddle with my cat. The main solution I usually hear is to (in Jackson Galaxy's voice) play with my cat. She is not interested. Yes, I do it the correct way, in complex patterns, imitating small prey and all that. I try training her, Kami reacts well, learned a few commands, but often not very interested, plus she is apparently not food motivated. I try taking her out on a leash, but I live in a big apartment building and she is scared of going anywhere further than the floor we live on, although she is very curious about the outside world. And, ofc, she hates the process of putting on the leash and often runs back into the apartment when sees me taking it. Walking without a leash is not an option - we live in a big and dangerous city. Calming cat pheromones that you plug into an outlet (or how that thing is called) didn't help.
She sleeps a lot, never destroys anything, very calm, but I am worried that if I ignore this it might turn into health issues. And I want to have a cat. For now she is a rarely seen polite ghost. Hense the name. What should I do?