I do not see anything immediate that would be useful. The only significant database appears to be off-line and the first available census (1861) would be too late. Some entries at:https://motty.lib.unb.ca/?q=list
February 16, 1813 McDonald David Marriage Gemima Bulyea?
February 16, 1814 McDonald Thomas Earle Son Baptism David & Jemima
January 1, 1816 McDonald Alexander Son Baptism Wickham David & Anne farmer
January 1, 1817 McDonald Mary Anne Dau Baptism Wickham David & Jemima born May 25, 1817, farmer
January 1, 1817 McDonald Rebecca Dau Baptism Wickham David & Jemima born June 9, 1817?, farmer
Perhaps Mary Anne is the Nancy you seek.