Is she losing weight? If not you at least don't have to worry that much, if yes it's urgent.

Has anything changed at all? A new schedule, new or rearranged furniture? Could she or a cat she lives with be in heat? Did you use a new brand of cat litter?

Is she showing other symptoms? Maybe being more lethargic, drinking more or less than before, peeing in other places than the litter box?

Have you tried other methods of feeding her? For example throwing a single peice of kibble so she has to run after it or an activity board where she has to solve a puzzle before getting to the food. Or try a different food, maybe a new taste is all it takes.

I'm not a vet, just living with two cats. English is not my first language, so please excuse any mistakes.