Gracie's items are seasonal. She'll rotate around the same stock (a specific Gracie series plus all the seasonal clothing) for about two and a half months, and then hold a sale where said items are priced lower and some additional items are added that are only available during her sales (the Card series plus some specific clothing). After the sale is over, she begins selling new items for the season.
Here's a link that shows her seasons and what items she sells depending on them.