The reason for which she has been most strongly criticized is her seeming lack of sympathy for Claudio when he pleads with her to save him by giving in to Angelo's desire. She turns upon him violently, revolted by his weakness. After a scathing speech in which she tells Claudio that he is no true son of their father, she leaves him in a rage, never to speak to him again in the play.
Isabella's supporters point out that looks and actions can speak as loudly as words, and the way in which brother and sister act in the last scene might substantially soften the earlier friction between them. They further point out that the kind of deep Christian conviction and commitment that Isabella had, in combination with a sincere fondness for her brother, would cause her no little anguish when met with Angelo's demands. Certainly she was under great emotional strain during the prison scene with her brother. Perhaps the wrath which she shows him is merely her way of bolstering herself to place religious convictions above love for her brother. Her genuine affection for Claudio might also explain her failure to react with horror upon learning of his crime. In going, first, to Angelo to beg mercy for Claudio, she expresses her conflicting feelings of disgust for the crime and love for the man:
There is a vice that most I do abhor,
And most desire should meet the blow of justice;
For which I would not plead, but that I must;
For which I must not plead, but that I am
At war 'twixt will and will not.
(II. ii. 29-33)
