Marilisa Poss is the wife of Nicholas Poss (Sr.) and is indeed his mother.
References: Rockingham County, Virginia Minute Book, 1778-1792, Part 1 1778-1786, by Constance A. Levinson and Louise C. Levinson (R. R. Donnelly & Sons Company, Harrisonburg, VA, 1985) p. 286 [437 of original] 22 August 1785 Nicholas Poss and wife Marilisa sold tract to Jno. Ayler witnessed by Jno. Tanner, Ronamis Dike, and Anthony Ailor. p. 287 [438 of original] Last will and testament of Nicholas Poss by Isiah Curry and Jno. Tanner. The executors therein named refused the execution and the widow relinquished her legacy left to her by her husband and chose her third, administration with the will annexed was granted to Heironimus Dike. Isiah Cury, John Tanner, Leonard Painter and Michael Deck or any three were to appaise the estate and Negroes if any of Nicholas Pos.