Who was Ella Kaye? What implication was made about her visit to Cody, and what did she do to Gatsby?

Ella Kaye was "a newspaperwoman" who ingratiated herself into the life of multi-millionaire Dan Cody, Jay Gatsby's first mentor.  It is implied that she somehow gained influence in Cody's life and acted in an advisory role similar to Madame de Maintenon, the unacknowledged wife of Louis XIV of seventeenth-century France. Cody, with Jay Gatsby as his factotum, sailed around the world on his yacht for five years until docking one night in Boston.  Ella Kaye boarded Cody's Tuolumne, and a week later, Cody was dead.  The implication is that Kaye had somehow caused, or at least hastened, Cody's death.  Dan Cody had intended for Jay Gatsby to receive $25,000 in his will, but Ella Kaye used a crafty attorney to acquire all of Cody's remaining wealth--in the millions--including the small legacy intended for Gatsby.

Fitzgerald, F. Scott.  The Great Gatsby.  Charles Scribner's Sons, 1925.