Mary could be
Mary Ann Nix
1805–1858
BIRTH ABT. 1805 • St. Ives, Huntingdonshire, England
DEATH 1858
Father Waddelow Nix
1776–1832
BIRTH 10 SEP 1776 • Coveney, Cambridgeshire, England
DEATH 1832 • St. Ives, Huntingdonshire, England
Mother Mary Anne Wasdale
1780–1846
BIRTH 1780 • St Andrew, Holborn, Middlesex, England
DEATH JUL 1846 • St. Ives, Huntingdonshire, England
Thomas Edward Watson
1807–1859
BIRTH ABT. 1807 • New Bottle, Durham, England
DEATH 11 MAR 1859 • St Ives Hall, Huntingdon, Huntingdonshire, England
husband of 3rd great-aunt
If you have access to Ancestry see my Tree "Brian Gilbert Family Tree" Mary Ann was the sister to my 2 x Great Grandfather John Nix.