I think Reeba's post is relevant as far as the difference between defending novels in general and how readers could get too caught up in them and forget reality.

As for Catherine, I felt sort of let down by her behavior in this part, as you did, Phil, and felt how mortified she had to have been when Henry "caught" her in this morbid fantasy. However, I think the experience taught her a lesson, even though she did display a lot of immaturity here. However, that is the beauty of JA's characters - they are not perfect, and I don't think she is saying anything about the gullibility of women in general. It would have been more unrealistic, would it not, if Catherine had ALWAYS shown herself to judge people maturely and show strength of character? Especially after being "told" about her immaturity and relative lack of intellect at the very beginning of the novel. She is only 17 when she goes to Northanger - maturity is a lengthy process!

Also, she had noticed the general's sometimes autocratic behavior and sudden changes in temper, so her suspicion of him combined with the influence of her favorite novels contributed to her flight of imagination, working herself into a frenzied fantasy about the general hiding a horrible secret. Although embarrassing to Catherine and shocking to Henry, I think he was sort of amused by it as well.