She is married to John Galt.
They got married on November 27, 1795 at Tarbolton, Ayrshire, Scotland.Sources 1, 2
Event (Proclamation of Marriage) on November 13, 1795 in Craigie, Ayrshire, Scotland .Source 2
The book describes part of the authors life, visiting various family residences, on her travels around Ayrshire. Jean/Jane Stevenson's Grandmother, Mary Galt, is Jean Galts sister, her Great Grandmother is Helen Young, Great Grandfather is John Galt.
GALTJOHNMARY KNOX/FR164 (FR164)13/11/1795584/ 10 298Craigie
GALTJOHNMARY KNOX/FR399 AND 477 (FR399)27/11/1795619/ 20 183Tarbolton
GALTJOHNMARY KNOX/FR399 AND 477 (FR477)27/11/1795619/ 20 111Tarbolton