Please remember than in her novel defence a few chapters later, Austen describes Cecilia as one of the better novels in the English language. So in creating Catherine as a refreshing parallel to traditional heroines of sensibility like Cecilia, I wonder what Austen was trying to say. I think possibly she was using this stereotype for comic effect. In reality, she knows these novels of sensibility - or at least the best ones, like Cecilia, Camilla and Belinda, have much more for them going than that - but she is able to make fun of them as a mark of her esteem, almost. She wouldn't be able to ridicule them unless she had read them. And she seems to have read widely in the genre, because she seems to know all the expected attributes of the heroines, as outlined and lacking in Catherine in the first chapter.