Gracie will randomly start visiting the player's town once they have upgraded the Nookling Store to T.I.Y. and have spent at least 70,000 bells there. She will be found at the town's Plaza and when spoken to will express an interest in opening a shop in the town. The condition is she has to deem the player fashionable enough to meet her standards.
Gracie's Fashion Check
The player will be asked to complete a fashion check. Gracie will give a theme and the player must put together an outfit that matches the theme. If the player does not have clothing items that fit the theme, anything that does not clash with the given theme is okay. Gracie will decide if the player's outfit passes her Fashion Check or not. She will reward the player with a piece of clothing or furniture if they pass. Once the player has passed the Fashion Check four times, Gracie will acknowledge the player's fashion sense and decide to set up shop in town.
Upon unlocking the T&T Emporium, Gracie's shop will be found on the 3rd floor.
Please click here for more details about the Fashion Check and the theme sets.