Elizabeth and Abigail are highly contrasting figures in the play.
Elizabeth is rather meek, though "passive-aggressive" with her husband. She is hurt. She is honest. She is upright and loyal.
Abigail is very much the opposite in all of these areas. She is aggressive. She is domineering. She is dishonest and she will sever ties with anyone or betray anyone if she might gain from doing so in any way.
As a trope, we can see these two characters as reflections of Proctor's two sides and symbolic of the nature of his dilemma in the play. The conflict between the two women mimics the conflict within John Proctor. It is only when Elizabeth becomes strong enough to forgive John that he becomes strong enough to forgive himself and to act on his values without fear of consequence.