Catherine has already heard from James that his marriage with Isabella has been called off, because she is presumably going to marry Frederick Tilney. Now, after it has become clear to Isabella that Frederick will not propose to her, she writes to enlist Catherine’s help to salvage her relationship with James. In this context, and set down in a letter where each statement can be carefully considered, Isabella’s true motivations could not be any more transparent. For instance, when Isabella writes that “many girls might have been taken in,” she suggests that, in her place, anyone would have believed that…