A domestic cat may not finish eating its food for three reasons.
Firstly, it could be stress. Cats, like people, lose their appetite due to stress.
A possible move, a visit to the vet, or the appearance of a new person in the house can affect the behavior of the furry one.

If a cat hides, meows loudly, or ignores the litter box, then the pet is probably scared and is telling its owners about it.
Secondly, the food may be spoiled. Cats will never eat anything that smells bad.
Therefore, it is better to keep wet food in the refrigerator, and leftover cat food should not be stored for more than 4 hours due to the risk of poisoning.
Thirdly, instincts push cats to hoard food.
Domestic cats do this too, even though their food is always in a bowl.
If your cat doesn't finish her food, just watch her, and perhaps you will understand the reasons for this behavior.