David Stevens provided the following: 1) I believe Ann was born in Danbury, Fairfield, Connecticut, rather than Floyd, Oneida, New York, in 1724; 2) Her mother was Sarah Ann Forward and not Anne Forward. Both were married to Benjamin Barnum and both had a daughter named Ann Barnum. The second Ann Barnum was born in 1744. Her mother was Anne Forward. I have been doing research on Ezra Stevens, born 1724, a direct ancestor who was married to both of these Ann Barnums, the first in 1744, the second in 1764.
The death date of About 1749 comes from family lore stating that she died shortly after the birth of her son Ezra G. Barnum, who was born in 1748. The addition of her son Samuel, born in 1750, suggests that there might have been some substance to the family lore but the date was incorrect. It's common in genealogical research to find family lore only partially correct.