Tabitha b. 12.25.1749
FROM "Genealogy of the Ela Family" by David Hough Ela, pub. 1896.
She is listed as married to Richard Petty, Thornton NH; perhaps this was another marriage. Tabitha's parents listed same as you have. They removed from Haverhill MA to Londonderry NH ca. 1755. Samuel was in the army, 1775. Samuel b. 27 Feb 1724/25, d. 1784. Nine children listed.
Ancestral line shown as Tabitha> Samuel>Samuel>Israel of Haverhill.
This book can be found in several larger genealogical collections if you want more details.