This woman espoused an evil political ideology that she sought o impose on the world under the false pretense of “justice”. I know she had an abortion, which I have less of a problem with since one can regret, repent, and receive forgiveness, but as far as I know she never repented of her communist ways.
She never did repent of her Communist ways, and she praised her Communist friends in the “Catholic Worker”; see http://dorothydayworker.blogspot.com/2012/05/dorothy-day-catholic-communist.html for documentation.