Over the course of the play, Mary Warren nearly changes, as develops new traits the stem from her experiences in at the trials. However, in the end Mary Warren regresses and her part in the story ends as it began, in meekness and acquiescence.
Mary Warren is the Proctors' servant who seems timid and subservient but who finds a powerful role in a kind of people's jury in the courtroom.
Early in the play Mary Warren is seen as the frightened and meek member of the group of girls. She recommends that they admit what they have done to avoid larger trouble. She is immediately defeated by Abigail in this effort and made to agree with Abigail's story under threat from Abigail.
As the trials get underway, Mary Warren defies John Proctors orders and attends hearings as a witness. The experience flushes her with a new sense of power. She feels that she no longer needs to be as meek as she had been. Her rebellion ends when Proctor convinced her to speak on Elizabeth's behalf at court, admitting to the fraud that the girls have committed.
At court, Mary Warren attempts to be strong and to buck the authority of Abigail by telling the truth. Abigail is too strong for her, however, and Mary Warren's brief development of strength and defiance is ended. Abigail dominates Mary Warren with an ingenious deception, acting as if Mary Warren were haunting her with a spirit.
This threat is understood by Mary Warren. She will be accused and convicted of witchcraft if she persists in telling the truth. Yet, she will have a chance to save the life of Elizabeth Proctor with the truth.
In order to tell the truth in the face of Abigail's threat, Mary Warren would have to truly be strong. She would have had to actually change and mature in the story. This change has not taken place on a deep enough level, as Mary Warren's actions prove. She relents and saves herself.