Catherine was unable to trust her own perceptions and form a negative judgment of the General when she first met him. She now swings to the other extreme, assuming he is a tyrant who made his wonderful wife’s life miserable. This idea does not come out of nowhere: in
The Mysteries of Udolpho, the villain Signor Montoni brings about his wife’s death by mistreating her. Catherine can seemingly only conceive of the world as split into two camps: the humdrum and morally perfect people she knows, and the dramatic, potentially evil characters to be found in Gothic novels. She now decides that the General may fall into the latter camp.