Mrs. Macy is Susanna (Coleman) Macy, aged 45.B. 5 Oct. 1769, prob. in Nantucket, eldest offspring of Seth and Deborah (Swain) Coleman, of Nantucket and Dartmouth. M. 1 Jan. 1790 at Dartmouth to Edmund Macy--b. 5 May 1766 in Nantucket, d. at sea ca.1809--son of Stephen and Mercy (Allen) Macy, widow of Prince Coffin. Both Susanna Coleman and Edmund Macy had come to Dartmouth with the Quaker Whalers; but after the collapse of the whaling industry at Dartmouth, they were among those who chose to return to Nantucket--which they did shortly after the birth of their second daughter Elizabeth (b. 30 June 1797 at Dartmouth).
Elizabeth is very likely the Miss Macy referred to--despite the fact that at age 18 she appears older than Louisa's description of her as "a nice little girl" (see S26); for, as Elizabeth Macy has no younger sisters still living, the description would seem to apply to a perhaps petite appearance and girlish look rather than to her age.
The removal of the Macys from Dartmouth when Elizabeth was a baby would explain why Louisa does not appear to be well acquainted with the young woman. But she quickly forms a good opinion of her (see S26). It seems that Mrs. Macy and her daughter are in Dartmouth on an extended visit and staying at Mrs. Macy's father's--see S22 and S22n3 . Although Miss Macy is the cousin of George, James, and Eliza Coleman (her mother being John Brown Coleman's sister), she is not directly related to Louisa--who also is cousin to the Colemans. (Elizabeth Macy m. Alexander Hussey. Susanna (Coleman) Macy d. 12 Oct. 1833.)