Mrs. Marwood is not carefully drawn. The mistress of Fainall, she loves Mirabell. Hypocrisy is a necessary part of the way of their world for everyone, but it is the most significant characteristic of Mrs. Marwood.
We first meet Mrs. Marwood talking to Mrs. Fainall. Both women speak hypocritically, both are engaged in delicate maneuvers designed to gain information but to reveal none, both are suspicious. Mrs. Marwood is hypocritical in her relation with Fainall. She can pretend to be wholeheartedly and unreservedly in love with him, while actually she is disguising her feelings for Mirabell, not with complete success. Her disguised love for Mirabell is an important motivation in the action. It is one-although only one — of the reasons why she encourages Fainall in his plot. When Millamant insults her, taunting her with love for Mirabell and her greater age, she is like the traditional villain of the tragedies of the period, revengeful because her vanity is offended.
But Mrs. Marwood's essential hypocrisy and villainy show up most clearly in her relations with Lady Wishfort. Here she feigns friendship. She tries to spoil Mirabell's plan; as confidante and adviser, she tries to get Lady Wishfort to accede to Fainall's demands. There is, in short, no one on the stage with whom her relations are not based on an important lie.