Isobel Menzies Silver.
Isobel Menzies Silver (1860-1934) lived with her brothers at Harvieston Farm before getting married later in life (aged 46) to a widower named John Duncan, who was the brother of Alex Duncan who’d married her eldest sister Helen and moved to England.
There is a 1930 letter she wrote to her Australian niece Bella Dobbs (nee Silver).