I think this group of chapters really shows Catherine starting to trust her own judgment and her own good sense. Two quotes from chapter 9 show this:

Catherine listened with astonishment; she knew not how to reconcile two such very different accounts of the same thing; for she had not been brought up to understand the propensities of a rattle, nor to know to how many idle assertions and impudent falsehoods the excess of vanity will lead.....She reflected on the affair for some time in much perplexity, and was more than once on the point of requesting from Mr. Thorpe a clearer insight into his real opinion on the subject; but she checked herself, because it appeared to her that he did not excel in giving those clearer insights, in making those things plain which he had before made ambiguous;

Then:

Little as Catherine was in the habit of judging for herself, and unfixed as were her general notions of what men ought to be, she could not entirely repress a doubt, while she bore with the effusions of his endless conceit, of his being altogether completely agreeable. It was a bold surmise, for he was Isabella’s brother; and she had been assured by James that his manners would recommend him to all her sex; but in spite of this, the extreme weariness of his company, which crept over her before they had been out an hour, and which continued unceasingly to increase till they stopped in Pulteney Street again, induced her, in some small degree, to resist such high authority, and to distrust his powers of giving universal pleasure.

Then just at the end:

...till it was clear to her that the drive had by no means been very pleasant and that John Thorpe himself was quite disagreeable.

Of course, this last bit is a bit influenced by the fact that Mrs. Allen has seen the Tilney's while she's been out on her carriage ride with the lout Mr. Thorpe.

But it does seem clear that she is starting to trust her own instincts and her good upbringing to make her own decisions.