This could definitely be normal, but it doesn't have to be. With cats, appetite is pretty sensitive to all kinds of things - stress, dental problems, a little upset stomach, or just that she's tired of the food. A week isn't super long yet, but if Luna otherwise seems fine, uses the litter box normally, and still plays, I'd just keep an eye on it for now. Some cats just go through phases where they eat less, and that's no big deal.
What I'd do in your place: Check if maybe she's eating somewhere else or still getting snacks you don't know about. And test if it's the food - try a different brand or warm it up a bit before serving, a lot of cats prefer that. My Luna went through a phase once where she suddenly stopped eating her usual brand, until I switched to something else.
But if this whole thing goes on for two or three weeks or longer, or you notice she's getting lethargic, hiding, throwing up, or anything else seems off, then I'd go to the vet. Tooth infections or other stuff could be the reason, and you should get that checked out. But right now I wouldn't worry too much about it, as long as she seems okay otherwise.