According to 1) The Knapp Family in America (p. 8), and 2) A History of the Chief English Families Bearing the Name of Knapp (p. 192) there were two Elizabeth Knapps that were 1st cousins.
The first was born 21 Apr 1655 to James Kanpp and Elizabeth Warren of Watertown & Groton, Mass. Both histories state that she married Ephraim Philbirck. The Knapp Family in America states that she was bewitched in 1671. Neither source lists a marriage date. Nor do they list any children
The second was born 23 Jul 1657 to William Knapp (brother of James Knapp mentioned above) and Margaret _____________ of Watertown, Mass. Both histories state that she married Samuel Scripture. The first source states that he was from Cambridge and they married on 11 Sep 1674. Neither source lists any children, but there are ample sources that list the descendants of this marriage.
My hypothesis is that Samuel Scripture's Elizabeth Knapp was not the witch of Groton, but instead was the cousin of that Elizabeth Knapp. Because the Groton witch is so well documented and of such interest to historians and genealogists alike, most genealogists assumed that she was the wife of Samuel Scripture, that they had ten children, and ultimately thousands of descendants. I submit that both histories above are correct, and that the Groton witch married Ephraim Philbrick, likely had no children, and died not long after marriage. Possibly Ephraim Philbrick married second Elizabeth Baron.