At the end of the novel, Eliza decides to run away from home out of shame over her illegitimate pregnancy, leaving behind a letter explaining the situation to her mother. Describing Mrs. Foster's discovery of the letter, Foster uses dramatic language that appeals to the reader's feelings, making the scene a good example of pathos. When Mrs. Wharton first reads the letter, she exclaims,
[...] dear, very dear hast thou been to my fond heart! Little did I think it possible for you to prepare so dreadful a cup of sorrow for your widowed mother!
Even within a novel written in a formal tone, the emotive language and frequent use of exclamation marks distinguishes this scene from others before and after it, signaling that this is an especially dramatic moment of Eliza's story. Likewise, the fact that Mrs. Wharton directly addresses the absent Eliza underscores their separation and causes the reader to acutely feel her maternal grief.
On a first read, the content of Mrs. Wharton's speech reflects her own adherence to social rules of female behavior, and her distress that Eliza has violated them so dramatically. Describing herself as a widow, she stresses her vulnerability and her loyalty to the institution of marriage; describing Eliza's situation as a "dreadful cup of sorrow," she characterizes the out-of-wedlock pregnancy in extremely negative terms. The stress Mrs. Wharton places on her own virtue probably invoked the sympathy of contemporary readers who, like many characters in the book, would have judged Eliza's behavior harshly.
At the same time, Mrs. Wharton also expresses unconditional love for Eliza, despite her social trespasses. After recovering from the initial shock of the letter, she wonders aloud,
[...] where can the poor fugitive have fled? Where can she find that protection and tenderness, which, notwithstanding her great apostacy, I should never have withheld? From whom can she receive those kind attentions, which her situation demands [...]
In this passage, Mrs. Wharton shifts from considering her daughter a source of "sorrow" to a "poor miscreant." She also declares that despite Eliza's "great apostacy," or transgression, she is still willing to care for her through her pregnancy. Given the strict standards of female chastity in post-Revolutionary America, and the social ostracism facing women like Eliza who violate those norms, this is a radical statement indeed: Mrs. Wharton is saying that Eliza's status in the eyes of society has no bearing on her love as a mother. Ultimately, the use of pathos and Mrs. Wharton's initial invocation of conventional social norms encourages the reader to sympathize with Eliza and allows Foster to smuggle a message of unconditional love into a novel that, on the surface level, endorses conservative ideals of female behavior.