I chaulk it up to the imposing personalities of the Thorpes. They never really listen to Catherine or seem to know her at all. John Thorpe starts off planning Catherine's daily activities for her to amuse himself with silly rides, assumes she is hers for dancing without asking her, and doesn't seem to care about anything she says. Isabella is always proclaiming that Catherine knows what she is thinking, when Catherine clearly has no idea. They attempt to thwart her plans with the Tilney's time and time again. They seem to think the world revolves around them and their ideas. John thinks Catherine encourages him in his 'proclaimations' of affection and doesn't see that she is absent-mindedly answering his questions because he doesn't see her, he only sees what he wants!