My research leans toward Joanna Williams being "Joanna Willems Neering", one of 4 daughters of John Williams, aka Jan Willems Neering, of New Castle, a prosperous merchant. His wife was Anna Catherine de Meyer.
I believe - because I can't ever find anything to prove it - that Joanna was NOT born in Rhode Island and that it is an error of long-standing. Wishful thinking that she was a granddaughter of RI founder, Roger Williams. There is no child named Joanna of Lydia Olney and Joseph Williams and it is very unlikely that the Ross family wouldn't have proudly proclaimed her Williams/RI heritage.
A very interesting clue, but not proof, is that a portrait of Joanna W. Neering brother, Jacobus Willems Neering, was passed through the Ross/Read families - see this link:
https://nc-chap.org/portraits/details.php?wname=jacobus_williams
The notes with this link say:
This portrait descended through the Ross and Read families to the present owner. It is believed to be that of Jacobus Williams, brother of Joanna Williams, first wife of Rev. George Ross.
The identity of the sitter is more than a little murky, since there is another upper-class brother-sister pair with similar names that lived in New Castle during this period: Jacobus Williams Neering (or Nerring) and Joanna (or Johanna) Williams Neering. It is not obvious whether they are the same or not.
Jacobus and Johanna Williams Neering [Nerring] were children of John Williams Neering according to the Calendar of Wills, New Castle County, 1682-1800.
John Williams Nerring. [Neering?] Merchant. N. C. [d] June 4, 1698. Aug. 27,
1700. Misc. 1, 366. Son, Jacobus Williams Nerring; four
daughters, Sarah, Lydia, Elizabeth and Joanna Williams Nerring.
Wife deceased. Adm. daughters, Sarah and Lydia; Mr. Richard
Halliwell; Dr. Samuel Staats, Capt. Johannes Kip.
John was the second wealthiest person in the New Castle Constabulary according to the tax assessments from 1683.
According to the NY Genealogical and Biographical Record, Jan Willemse Neering of New Castle married Ann the daughter of the former mayor of New York. He was a member of Penn's provincial council. He was also known as John Williams.
"Jacobus William Neering" m Mary Garland in 1715 according to the Immanuel's Vital Records. But it provides no details of children or death for either them or Joanna Ross. Johanna's [Joanna] marker inside the church has the inscription: "Memor virtutum Johannae conjugis Honesto genere natae hoc sepulcri Monumentum maritus Georgius Ross. Evangelii praeco, extruendum curavit. Anno acquievit illa aetatis trigesimo Septimo. 29 September 1726." "Dixit ei Jesus quisquis vivit et credit in me non morietur in eternum." "Calcanda semel via lethi."
Joanna is an unresolved discrepancy. The "Rossiana" book of Read/Ross genealogy says of the wife of George Ross. "Joanna Williams b. 1680 Rhode Island d. 29 Sep 1726 Buried: Immanuel Church, New Castle, DE".
If you find any proof of Joanna's lineage, I'd love to know. I'm the 6th Great Granddaughter of George Aeneas Ross and Joanna Williams.