Hi Dave
Assuming she married a Joseph Williamson in 1877, NSW... The death index indicates her father is David.
Australia Death Index, 1787-1985 about Sarah
Name: Sarah A Williamson
Death Date:1913
Death Place: New South Wales
Father's Name: David
Registration Year: 1913
Registration Place: Parramatta, New South Wales
Registration number: 18517
Geoff