We've talked about Catherine being a 'normal' girl, and her dislike of learning, and I wanted to expand on the description of CM in ch 2:

her manners just removed from the awkwardness and shyness of a girl... her mind about as ignorant and uninformed as the female mind at seventeen usually is

This sets up CM's ignorance, her dislike of learning, and her habit of being unsure in company as a result of youth and inexperience. This also gives the hope that like all young people, she will hopefully learn and improve.

Compare CM to other young 17-18 yr old characters is JA, such as Fanny Price, Kitty Bennet and Harriet Smith - these girls are all a little awkward, but they grow and develop as the novel goes on.