In the VA State Archives, for Faquier Co., VA, there is a will for Francis Southard, dated 1779 - in this willit mentions, wife Mathew, and daughter Sarah, the wife of Nathaniel Dodd.
This still doesn't clear up the mystery of wife Sarah Allen - but it gets us a little closer.
I am also a descendant of Allen Dodd & Mary(?), through 2 of his children; Susannah Hannah Dodd, (5 Dec 1778-8 May 1868) who married Drury Price (28 Feb 1782-25 Nov 1856)and Nathaniel Dodd, (1783-????) who married Elizabeth Perkins (1784-????).