hi Rockland15, you have probably worked out my descent from the messages posted on this site- but briefly it is from your Sarah's father John Diamond who landed in Sydney, January 1857 on the Matoaka (parents William Diamond & Elizabeth Addies of Wigtonshire) and married Mary Little in November 1857. Mary was an immigrant from Langholm, Dumfries, immigrated 1853, followed by her younger sister Jane Little (later Charlesworth) in August 1857, just in time to be a witness at Mary's wedding. My ancestor is son John born Sydney, 1865 (married Mary Ann Cole in 1887) leading to son William James born Parramatta, 1888, followed by his son William John in 1910, his daughter Lorna in Sydney, 1932... and so on.
I knew from records of your Sarah being born in the Braidwood area in 1858 and thought how this was unusual and quite a pioneering venture for John & Mary. Of course they were back in Sydney by 1860 (Chippendale/ Annandale area, later Rookwood, later Norval St Auburn). I have a July 1884 newspaper marriage notice for Sarah Diamond of Rookwood to John McMillan (son "of Rev. Henry McMillan of Glasgow,Scotland). Her children, I think (from my notes) were John, James, Sarah, Elsie M, Mary, Florence E, Jessie, Laura J. but you may need to correct me.