She ruthlessly pursues this goal against Charles Darnay, his wife, Lucie Manette, and their child, for crimes a prior generation of the Evrémonde family had committed.
She refuses to accept the reality that Charles Darnay changed his ways by intending to renounce his title to the lands to give them to the peasants who worked on them.
Her consuming need for revenge against the Evrémonde family, including the innocent Darnay and his wife, brings about her death by her own weapon at the hands of Miss Pross.
[1] Defarge's desire for revenge ultimately stems from the rape of her pregnant sister at the hands of the aristocratic Evrémonde brothers, and Teresa Mangum therefore suggests that "the logic driving her story is that the secret crime of sexual violence against women fuels the French Revolution".
Also, in the same movie, the villain Bane can be seen sitting and knitting (like Madame Defarge) in the audience of one of the "trials" presided over by The Scarecrow (Cillian Murphy).