See Emma's arguement to Harriet in chapter 7 "A woman is not to marry a man merely because she is asked, or because he is attached to her." Also Fanny in Mansfield Park to Edmund "I think it ought not to be set down as certain that a man must be acceptable to every woman he may happen to like himself" (chapter 35)

This echoes in Mansfield Park "when they first saw him he was absolutely plain, black and plain; but still he was the gentleman, with a pleasing address. The second meeting proved him not so very plain: he was plain, to be sure, but then he had so much countenance, and his teeth were so good, and he was so well made, that one soon forgot he was plain; and after a third interview, after dining in company with him at the Parsonage, he was no longer allowed to be called so by anybody" (chapter 5)

This sounds very much like Miss Crawford in Mansfield Park (far too many instances to quote)

See also Emma "A woman may not marry a man merely because she is asked, or because he is attached to her" (chapter 7) and Mansfield Park "I think it ought not to be set down as certain that a man must be acceptable to every woman he may happen to like himself" (Chapter 35)

This reminds me of Tom Bertram, the elder brother, responding to concern from his younger brother about the proposed amateur theatricals at Mansfield Park. "Manage your own concerns, Edmund, and I’ll take care of the rest of the family" (MP chapter 13). It feels very much like "I'm the older sibling, I know what I'm doing"

Another link to Fanny Price who also enjoys seeing the seasons pass in the country

You could compare Anne's predicted fate with that of Mrs Price in Mansfield Park. She married "to disoblige her family ... a lieutenant of marines, without education, fortune, or connexions" (Chapter 1 MP) and became "worn and faded, so comfortless, so slatternly, so shabby" (Chapter 42 MP). Perhaps Lady Russell was right to be concerned.

A similar sentiment is expressed by Fanny Price in Mansfield Park: "her wishes were overthrown ... she was so totally unused to have her pleasure consulted, or to have anything take place at all in the way she could desire" (chapter 28 MP)

Potential parallels to Mr Bennet's feelings for Mrs Bennett in Pride and Prejudice. Mr Bennet had been "captivated by youth and beauty, and that appearance of good-humour which youth and beauty generally give, [and] had married a woman whose weak understanding and illiberal mind had very early in their marriage put an end to all real affection for her." (P&P Chapter 42) Perhaps this also parallels Sir Thomas Bertram's feelings for Lady Bertram in Mansfield Park. It's never stated that Sir Thomas regrets his match but she "captivated" him (chapter 1 MP) and became a "woman who spent her days in sitting, nicely dressed, on a sofa, doing some long piece of needlework, of little use and no beauty, thinking more of her pug than her children" (chapter 2 MP). It seems more fitting somehow that it was the men making choices led my their hormones more than the women (though you must consider Lydia Bennet). Austen points out constantly how women had few choices in life and marriage, they had to make good ones as they would be trapped, they did not have the same freedoms as men.

The Miss Beauforts seem similar to Miss Crawford in Mansfield Park and Miss Isabella Thorpe in Northanger Abbey who were preoccupied with making an advantageous marriage by "capturing" or "captivating" a wealthy man.

Reminiscent of Henry Crawford's desire to make Fanny Price fall in love with him in Mansfield Park.

A common theme across Austen novels is that women tend to be more meticulous about writing letters than men. In Mansfield Park, for instance, Mary Crawford laments the fact that her brother Henry writes very short letters, if at all. Similarly, in Sense and Sensibility there is frequent correspondence between Marianne, Eleanor, and their mother. It is relevant that Austen herself frequently wrote letters to her sister Cassandra. Here is a sample of their correspondence: http://www.bl.uk/learning/timeline/item126754.html

  This chapter establishes familiar character dynamics that might elucidate the trajectory of the personas Austen presents in this unfinished text. The chapter begins with the introduction of Miss Esther Denham and Sir Edward Denham, a scheming sibling pair reminiscent of Mansfield Park’s The Crawfords and Northanger Abbey’s The Thorpes. Austen explicitly establishes the bald aim of the two to obtain wealth and status from advantageous matrimony, a characteristic that similarly mirrors the Crawfords and Thorpes. Sir Edward, in particular, resembles Austen’s past villainous men; throughout the Austen canon, coxcomb-esque behaviors are the cardinal sins of bachelors. Indeed, Willoughby, Wickham, Henry Crawford, Mr. Elton, Thorpe, and Mr. Elliot all receive biting characterizations by Austen, and thus, given the fates of these men in their respective novels, we can predict that Sir Edward is not the male love interest of this story. 
 Sir Edward’s dynamic with, and apparent longing for the affection of, Clara Brereton, additionally reverberate into the Austen canon in a meaningful way. Other Austen works present relationships between gentried men and pseudo-adopted young women; notably, Emma features Jane Fairfax and Frank Churchill’s secret engagement and Mansfield Park depict Henry Crawford’s arguably predatory pursuit of Fanny Price. These relationship both demonstrate wealth and class incongruities as interpersonal complications. Further, these dynamics are also characterized by the ignorance of other characters to the details of the relationship. Therefore, we cannot know from this unfinished account of Charlotte’s observations if Clara Brereton is a Fanny Price or a Jane Fairfax; we cannot fully know if the behaviors and dispassion Charlotte Heywood witnesses are evidence of a painful resistance to unwanted advances or red herrings to disguise an intimacy. Since speculation is the nature of this activity, however, it is notable that in both Mansfield Park and Emma, outside perceptions of the aforementioned relationships were incorrect. Therefore, paradoxically, Charlotte’s perception of Clara’s distaste for Sir Edward might in fact evince a returned affection and eventual marriage between the two. 

I predict that this character will be relevant to the marriage plot. The idea of a young person in this kind of circumstance reminds us of the Crawfords or Catherine Moreland. Single individuals living with relatives have, in other Austen novels, been very relevant in the marriage plots.

Links to common words/themes throughout the annotations