Did she always live at Dunham?
Mary married Henry, Lord Grey of Groby (later 4th Earl of Stamford) in 1736, when he was 20, and she was 32. Despite her parents having a contentious marriage, they were, as far as we can tell, a loving couple. She lived at Bradgate Hall in Leicestershire, before moving to Enville Hall in 1739 and began to build a home together as the new 4th Early and Countess of Stamford. Harry and Mary began to rebuild Enville, much like her father had done at Dunham; she lived here until 1758.
What happened after she returned to Dunham?
She was 54 when her father died, and Dunham Massey was given to her. She efficiently managed the tenants, the farmers, the household, the accounts and some farming innovations. She supported, financially and practically, new schools, chapels and hospitals alongside finding advantageous marriages for her children. She personally negotiated with the Duke of Bridgewater’s agents to ensure that the building of his new canal had every advantage to herself and her tenants.
In her final years, mainly spent at Dunham after Harry died in 1768, she enjoyed a life with her children and grandchildren while continuing to run the estate and pursue her interests.