I agree that the rumor about Esther's maiden name being Mitchell probably arose from the Will of John Mitchell which you cite.This Will was written 23 Sept. 1780 and proved in Augusta Co., VA on 15 April 1783.
This will does not indicate that John Mitchell had any wife or children.He make the following bequests:
1.Ann Russell - 150 pounds
2.Mary Russell - 150 pounds
3.Andrew Russell's children - 100 pounds each, Ann, Mary and Matthew to receive their 100 pounds immediately and William, Betty, Andrew, John, Jean & James when they are of age.Various items of personal property were also given to these children of Andrew Russell.
4.Esther Turk - 100 pounds, Thomas Turk, her father, to hold it until she comes to age.
The witnesses were John Reaugh, Margraet Kirk and Mary Turk.Mary Turk was probably Thomas Turk's second wife, born Mary Gleaves, mother of Esther Turk.Mary (Gleaves) Turk was the eldest daughter of Matthew Gleaves, Sr., and Esther __?__.
There is a Matthew Gleaves who obtained a marriage license in Lancaster Co., PA in 1745.I think this is where and when Matthew Gleaves, Sr., married Esther __?__.
One would think that if John Mitchell were the father of the Esther who married Matthew Gleaves that he would have made some reference to Esther, who was then known as Esther Rafferty.If he had children at all, I would expect that he would have mentioned his children in the Will and described them as his children in the Will.
I have tried to find a link between the Russell family and the Turk or Gleaves family without success.I have tried to find a link between the Mitchell family and the Turk, Gleaves or Russell family without success.Although, Mithcell could be Esther's maiden name, this does not sit right with me.
Also, if he was related to Esther __?__, wife of Matthew Gleaves, Sr., why would he select out Esther Turk as the only one of several children of Thomas Turk and Mary Gleaves to leave a bequest to?Why would he not have left a bequest to all the children of Thomas Turk and Mary Gleaves equally like he did with the Russell children?
Matthew Gleaves, Sr., and Esther __?__ had daughters Esther and Elizabeth.I do not know who they married.Maybe one of them married Andrew Russell.Maybe one of them married John Mitchel and predeceased him.
If John Mitchell was a brother of Esther __?__ who married Matthew Gleaves, Sr., I would expect that his will would have mentioned his relationship to his beneficiaries.
I do not mean to say that Mitchell could not be the maiden name of Esther.In my opinion, the issue requires more evidence before one should pencil in her name as as a reasonable possibility.