Storytelling in Northanger Abbey

In this novel about reading, and writing, it is fitting that the first person narrator is in fact the author of the novel. While that first person voice comes through more frequently in the middle and the end of the text, we must be aware that she is the first person narrator throughout. When she allows this voice to come through, she is acting in two positions: an instructor to her reader's and a defender of the novel as an art form. While the commentary she provides in both areas are very interesting and a deserved focus of this text, I would like to trace the narrator's its effect on storytelling. This narrator is not a part of the story and her only relation to the characters of the story is that she is making them up and developing their stories.
Yet, throughout the bulk of the novel, Austen is acting as a third person narrator that can only know and see what Catherine learns and sees simultaneously. This gives us a picture into the interiority of Catherine (self-concious about her position in society and her position with Henry, yet also excited by adventures resembling the romances that she reads). However, when it comes to moving the plot quickly, Austen often abandons this close tie with her character of choice and moves all of the characters about like chess pieces. In particular, the last two chapters, Austen has completely abandoned Catherine in favor of a third person narrator that can see the actions of all characters, even if Catherine cannot. When she dives into the interiority, it is not Catherine, but a combined Catherine and Henry's interiority: "They felt and they depolored-- but they could not resent it." All throughout the text, Catherine would have died for an opportunity to know the sentiments of Henry, and now it seems that their sentiments are tied together and identical. I belive that this abandonment of Catherine is because in the interest of efficiency, staying close to the interiority of one character is not feasible.
Why follow Catherine as a narrator in this novel? For Nancy Armstrong, the true testament of the novel is to express the excesses of individualism and guage how such acts of individualism are received through the plot. Yet, I would argue that the characters that truly exhibit an excess of individuality are Henry (defying his father by marrying Catherine) and Isabella (actively attempting to engage in relationships that will alter her station in life). The plot effects vary, the one who acts out individuality for love is rewarded with happiness and the one who acts out individuality for greed is left in loneliness. Yet Catherine safely toes the line throughout the text and never acts out of incivility by her own doing. Even when she is outwardly scorned (John not stopping the carriage and General Tilney turning her out of the house) she does not retaliate at all or defend her position acively to those characters. So, why follow her, in this marriage of novel and individual?