I really like the sentence you quote because it shows that Catherine is quite an intelligent girl and a shrewd observer from the very beginning on.

During much of the novel we see her as naive, slightly limited and often mistaken, but this passage is proof of her intellectual capacity. Often, we get the idea that she's very good-natured but perhaps a little slow in the uptake, but I think that's wrong.
I seem to remember reading the introduction in question. It gives a very striking collection of instances of Catherine's being very able to think for herself, even challenging Henry (who usually knows best).