Abigail had a sister named Mary Cranch that died in 1811. It is possible she is speaking of her, though she also had another sister Elizabeth.
Collection: The Gilder Lehrman Collection, 1493-1859.
Electronic reproduction. Marlborough, Wiltshire : AM, 2014. Digitized from a copy held by the Gilder Lehrman Institute of American History.
Gilder Lehrman Institute of American History