I have the same problem with the adult stray that I rescued. The first couple of times I've been feeding the strays. she was the only one who would not eat at all. She was so skinny but I figured she probably finds food somewhere else if she refuses cat food. When I took her home, I tried training her to eat cat food. I would leave wet and dry food and nothing else. She did not touch the food for 2 days. I got so scared as she was getting pale so I gave in. I never tried giving her anything but scraps of chicken, beef, pork. She also eats vegetables and rice. I didn't know cats would prefer to starve than eat something they don't like.