I am wondering if all of your information is accurate.. I found Alzina Cummings in the 1880 census [Buffalo, NY] a widow, born 1838, with daughters Clara, born 1866 and Tina J., born 1872.
In the IGI, I found James Briggs, born about 1820, son of Ira Briggs and Diadana [that's how it was recorded], and Alzena Briggs, born about 1828 same parents...Westville Center, Franklin Co., NY.. Same reference showed an Ira Briggs married about 1809 in the same community to Diadana..and it gave his birth date as 20 March 1786 in Putney, VT.Checking that date for Ira Briggs lists his parents as Henry and Sarah.Other siblings were: Deidamia, born 1 June 1775, Putney Sylvester, born 13 August 1780/1 ditto Ira Warren, born 24 June 1788 ditto Matthew, born 24 November 1791 ditto
I also found a Henry Briggs married to Sarah Babbit on 18 June 1774 in Dighton, MA.Could have married and moved just north to southern Vermont.