Is it okay to feed my cat just once a day?

For most healthy adult cats, yes, as long as the total daily food amount is right and she handles the longer gap comfortably. That said, twice a day is the more common recommendation, mainly because a single big meal makes overeating and vomiting right after eating more likely, and a long overnight gap can trigger early-morning yowling for food in some cats. Kittens, senior cats and any cat with a history of vomiting or blood sugar issues generally do better on smaller, more frequent meals rather than one large one. If once a day is working with no vomiting, no begging and a stable weight, it is a legitimate choice, not a shortcut.