I'm quite confused to be honest. If she was the daughter in law of Jeremiah Connolly who died in 1879, then really, her surname should also be Connolly as she would have married one of his sons?
I assume (and you're really going to need some certificates here!) that Mary Colston is in fact the Mary Donovan who was married to Jeremiah Connolly, who then died, and then subsequently married James Colston? Am I reading this right? It's even more complicated than my lot who didn't believe in using a lot of different christian names and marrying their in-laws (causing lots of confusion).
If this is correct, then your Jeremiah's father could well have also had a father of the same name (who died in 1879 rather than 1889), and you may well have now gone one step back!
But this would suggest that she provided the author with this information about 20 to 30 years before he wrote the book as she was born circa 1859?? I'll speak to my gran - she's usually fairly reliable (after my grandfather corrects here), but you'll owe me for the hours of rambling she'll put me through!