Jordan Baker is a beautiful, yet detached woman in Fitzgerald's novel. For a brief moment, we think she and Nick will have an affair, but her connection to him is as insincere as her connections with everything else in life. Like Daisy, she seems to use people for her own enjoyment and ignores how her actions may affect them later on.
She is important to the plot of the text because through her gossipy nature Nick (and us as the reader) learn of Tom's affairs when she tells Nick that Tom keeps "a woman in the city" and the tragic tale of Daisy and Gatsby's love. When Nick first meets Jordan, she eagerly points out that he must know Gatsby because of the proximity of their houses- thus she is the first person to bring up Gatsby's presence to our protagonist.