I have been looking for instances which show Catherine is not stupid and,
"At once to insist upon having such a report universally contradicted."
Do forgive me if it happens to be someones focus, but the week is soon over and so I thought of writing this.

In CH 1 - 8;
1.
At her first meeting with Henry when discussing journals etc.
I think she did very well there. She was just a bit unsure, that is all.
Her comments were well expressed for so young a person.

“I have sometimes thought,” said Catherine, doubtingly, “whether ladies do write so much better letters than gentlemen! That is — I should not think the superiority was always on our side.”

Later;
“Upon my word! I need not have been afraid of disclaiming the compliment. You do not think too highly of us in that way.”

Catherine's thoughts about Henry's conversation with Mrs. Allen about Muslins.
"Catherine feared, as she listened to their discourse, that he indulged himself a little too much with the foibles of others."

2.
When Isabella carries on about Mr. Tilney, Catherine gave a very sensible answer.
“But you should not persuade me that I think so very much about Mr. Tilney, for perhaps I may never see him again.”

3.
The third instance where I find her very sensible, and able to think intelligently, and rationally was when she sees Henry Tilney at the ball with a woman, and concluded she was his sister.
At first she drew upon her experience;
"..he had not behaved, he had not talked, like the married men to whom she had been used;"

Then she rationalised.
"....he had never mentioned a wife, and he had acknowledged a sister. From these circumstances sprang the instant conclusion of his sister’s now being by his side; and therefore, instead of turning of a deathlike paleness and falling in a fit on Mrs. Allen’s bosom, Catherine sat erect, in the perfect use of her senses, and with cheeks only a little redder than usual.