How is this quote from The Great Gatsby important to the book? "She was dressed to play golf, and I remember thinking she looked like a good...

Nick Carraway, the narrator, describes Jordan Baker this way in the final chapter of the book.  He's just met Gatsby's father, buried his friend, and realized that he needs to go home to the Midwest now because the East had become "haunted" for him as a result of all of the interactions he witnessed among the Buchanans and Wilsons and Gatsby.  This description of Jordan says a lot about both her and Nick. 

Although they are meeting to talk, she is dressed for golf, implying that she wants to leave him with a very particular impression of her, as though she were trying to put her best self forward so as to make him regret his treatment of her (for which she is clearly bitter).  Her chin is raised "jauntily" as it had been the first time he met her, and she seems perfectly put together, "like a good illustration."  Jordan has clearly worked hard to make Nick miss her, and she is somewhat successful.  He says, "Angry, and half in love with her, and tremendously sorry, I turned away."  Jordan is as concerned with appearances as she ever was, and Nick, though he is "sorry," cannot bring himself to stay with her.  Jordan is too connected with the events here that haunt him, and her probable lie -- that she is engaged to another man -- makes her as brittle as the "autumn leaf" with which Nick compares her hair.  Nick cannot return to a time before he understood the things that he has come to know about Jordan and people like her.