Mary Warren
A servant for the Proctor household and an official of the court, Mary Warren has seemingly conflicting interests throughout The Crucible. How do her various roles influence her? How does she change over the course of the play?

Most of your information will come from a close reading of the actual play. Pay close attention to Mary's scenes in Acts 1 to 3.
You might also want to check out the following books:
Bloom,
Harold. Bloom's Reviews: Arthur Miller's The Crucible.
New York: Chelsea House Publishing, 1998.
Johnson,
Claudia Durst, and Vernon E. Johnson. Understanding The Crucible.
New York: Greenwood Publishing, 1998
Martine,
James J. The Crucible: Politics, Property, and Pretense.
New York: Twayne Publishers, 1993.