Hello Eric. I strongly advise you to join the Auchmithie Roots forum mentioned above by Kev61, where you will find separate threads for the Spink, Swankie, Cargill and Eaton surnames as well as very useful transcripts of the various censuses. And lots of distant cousins among the people who post there!
I can tell you that Isabella Ritchie Cargill who married Charles Coupar Eaton was born in 1891, the illegitimate daughter of Margaret Spink, who however married the girl's father John Cargill in 1895. Margaret Spink and her siblings were 2nd cousins of my own great-grandmother, another Margaret Spink.
You are related to what is probably the best-known of all Spink families, as they produced Robert Ritchie Spink, founder of the fish-merchants R.R. Spink whose products can be found in the best supermarkets, as well as the royal kitchens, and this man was also Provost of Arbroath in his time.
If you search for 61 Auchmithie in the 1891 census on Auchmithie Roots, you will find Henry Spink and his wife Isabella Ritchie living there with their children Margaret (your ancestor), Isabella, Henry and Robert (aged 6). This Robert Spink married an Elizabeth Cargill, and they were the parents of the abovementioned Robert Ritchie Spink, who married Euphemia Carstairs Brown of Anstruther in Fife.
Harry