I used
~this guide~ for Gracie's fashion checks.
To sum it up, each piece of clothing is categorized as Sporty, Cute, Iconic, Rock 'n' Roll, Official, Ornate, Flashy, Modern, Historical or Basic.
Just wear 3-4 pieces of clothing that are categorized as basic and she should pass you. Just don't wear any clashing themes or she'll automatically fail you. You're given multiple chances, so don't worry if you don't pass the first time.
Good luck. c: