[2] Her stepfather Simeon Lord held land in trust for Mary Ann and her brother, land that backed onto the Tank Stream and had originally been leased by their late father Captain John Black, where Mary Ann and her brother had been born, and where her mother had been living prior to her relationship with Simeon Lord.
[4] Mary Ann married at the age of 19 on 1 March 1821 at St Philip's Church in Sydney to Prosper de Mestre who was 12 years her senior, and a business associate of her stepfather Simeon Lord.
Prosper, a merchant like her stepfather, was a good catch, and the large family was well and luxuriously provided for, becoming an important part of the fabric of Sydney in the 1820s to the 1840s.
They added three wharves in 1854, in 1856 a Church of England on land she donated and with capital she largely provided, and established a steam-driven flour mill in 1856.
When the Shoalhaven River flooded in 1870 settlement began to shift from Terara to the Nowra site 3 kilometres (1.9 mi) west.
The Terara House and property was left to Andre and Etienne de Mestre, and the 7 girls each received a portion of land.
Mary Ann was buried on the Terara property next to her husband Prosper de Mestre on land that she had donated to the church.