It seems like we have been coming at this from both sides and hopefully met in the middle. You had referred Michelle Haeusler and she had contacted me with the possibility that her ancestor Elizabeth McMaster was a daughter of Archibald A. and Elizabeth on my web page. She recounted the story of Elizabeth a protestant eloping with a local Catholic and emigrating to Australia. The emmigrating Elizabeth was born during a gap in the Kilmactranny Church records, so didn't appear on my page. It seems very likely that Elizabeth's mother was Elizabeth Mitchell.
Did you know that Samuel's mother was Elizabeth Mitchell, or were you inferring that from other information? The dates certainly fit in. I would be glad to add Michelle's and your information to my web page once I get the time. It certainly brings the names on my web page to life to find out information about them.