Well, using some estate files I have made progress with parts of Elizabeth's trail.
The estate papers of Thomas Knowles (d. 1766 in Perquimans) document wife Elizabeth and children William, Sarah, Abner, and John Knowles. The same papers also establish that by early 1767 widow Elizabeth "intermarried" with Durant Barclift. These findings explain the Knowles and Barclift elements in the will.
Still trying to establish the father of her son Joshua Arnold (d. 1806 in Pasquotank).