Hi Ron -
Thank you for your response. I find it interesting that those in your Chalmers line were known for their height. My grandmother, Winifred Ruth MacKenzie, who was Isabella's grandaughter, married Wilmer Wesley Riesmeyer. In German Riesmeyer means "big or tall man". Although I do not recall either of them being extremely tall.
I also have been unable to connect Isabella to any Chalmers in Inverness. I will continue to work on this and if I find a Mary Chalmers, I will let you know.