Likely Ann Foster, aged 19.B. 26 Nov. 1795, dau. of Edward Foster Jr. and Sarah (Ede) Foster.
Or Ann's younger sister Jane, aged 17.(b. 21 April 1798)
Their older sister Mary is the Mrs. AIbro referred to in S27 (see S27n4) and O17.
Mrs. Ebenezer Allen Jr., the hostess of the party, is the mother-in-law of William Foster (b. 21 Nov. 1789, son of Edward and Sarah Foster). He was m. to her eldest daughter Elizabeth Semple Allen (b. 19 Oct. 1792) on 30 Oct. 1814. (Ann Foster was m. 10 Jan. 1820 to George P. Lawson. Jane Foster d. 4 May 1852 in Dartmouth.)