The leader of the girls is Abigail Williams. She has the most to gain if the girls are successful because she wants to get rid of Elizabeth Proctor so she can marry John Proctor. Unfortunately, once the accusations begin to fly, the residents of Salem also use the accusations for their own benefit and Abigail loses control of the situation. This results in the death of John Proctor and her flight away from Salem. Mary Warren is a follower, not a leader, and of the group of girls making the witchcraft accusations. Abigail is able to use Mary when she makes the poppet, sticks a needle in it and gives it to Mary in order to accuse Elizabeth Proctor of being a witch. When John Proctor takes Mary to court to tell the truth, she is so afraid of Abigail, that she recants her testimony, and then rejoins the group of girls who are supposedly seeing a "spirit" in the form of a yellow bird in the room.
Abigail Williams is the obvious leader. She is headstrong, smart, and very manipulative. She knows right from wrong, and twists is all around to her benefit. She admits what they were doing in the forest to John Proctor, but threatens the other girls to stick by her by using the fear of being tried and hanged as witches. They both love and fear her. The admire her strength and want to be more like her instead of bowing down to the strict way of life of the Puritans, but they also fear the law of the community in which they live...partly because she uses it to her advantage to get them to do her bidding.
Mary Warren is not as strong as Abigail, but she also knows the truth of the matter. She is stronger than the other girls who blindly follow Abigail's lead. However, Mary is only strong in her conviction when John Proctor is there beside her. She loses her strength and the will to tell the truth in the presence of Abigail and the other girls. Her desire to be accepted by the Abby and the other girls is much stronger than her desire to please her employer, John Proctor.