On 5 June 1762 she married James St John Jeffereyes, a landowner who owned extensive lands including Blarney Castle.
She had fickle political sympathies, including supporting the Rightboys in County Cork in the late 1780s, allowing them to meet on her estate.
She championed the artist James Dowling Herbert, and even when he considered abandoning painting for acting, she found him a position at a London theatre company.
Despite the wealth her husband left her, Jeffereyes had financial difficulties, and in 1790 she was threatened with eviction from a house she rented and was only saved from this by her brother, who wanted to avoid any embarrassment.
Later the same year, she attempted to secure the post of adjutant general for her son-in-law, Col. Stephen Freemantle, but this was refused by King George III.
She found herself with increasing financial difficulties, appealing to the Dublin Castle administration for a pension in 1807, claiming that she saved Clare from a mob in 1795 while disguised as a kitchen maid.
Jeffereyes is mentioned in Richard Alfred Milliken's song The groves of Blarney which lauds her as "Lady Jeffreys that owns this station/Like Alexander or Queen Helen fair/There's no commander throughout the nation/For emulation can with her compare".