What does Jordan Baker's leaving "a borrowed car out in the rain with the top down" and her golf tournament "scandal" reveal about her?

One of the primary themes of the novel is carelessness of
people in general, but especially the upper classes.  There are numerous examples of
shallow, careless behavior throughout the novel.  There is the description of guests
behaving with a "simplicity of heart" as if they were in a an amusement park.  There is
the car accident scene at the end of Chapter Three.  There is the behavior of party
guests at Tom and Myrtle's flat in Chapter Two, and of course, there is the ultimate
condemnation of behavior in the novel when Nick decries Tom and Daisy in Chapter 9,
"They were careless people, Tom and Daisy—they smashed up things and creatures and then
retreated back into their money or their vast carelessness, or whatever it was that kept
them together, and let other people clean up the mess they had made. . .
." 

Jordan's behavior is just one more example of careless
people who don't consider the consequences of their behavior.  Remember, Nick is in
search of a world at some sort of "moral attention."  The people of the East certainly
are not a part of that world.