Miss Trotwood is, as stated, the aunt of David Copperfield, who at the time of his birth, blew him off upon discovery that he was not, in fact, a girl. As a partner in a scorned love affair, Betsey Trotwood is against women getting married, and is extremely critical of the men and women who choose to do so. Her hope, with this potential niece, was to raise her as independent, and not in need of a male counterpart.
When David, at a young age of about nine or ten comes to her for help against his step-father, Mr. Murdstone, Betsey Trotwood steps up to the occasion and takes David under her wing, however, begins to refer to him as Trotwood. For the rest of the novel, David Copperfield is known as Trot Copperfield. Betsey, in raising David and seeing his treatment of women, comes to relax her ardent negative ideals about the institution and provides her support in both his marriage to Dora and to Agnes. She warms her heart to David and in doing so, relaxing some of her prior seemingly crazy attributes, including becoming friends with Peggoty. She never does lose all her craziness though, and it helps make Betsey the comic relief during some of the more intense passages in the novel.
Betsey Trotwood is an essential character in helping David understand his life and she helps to shape the person that he becomes.