Margaret's family is mentioned in the book All Call Iona Home - the genealogy of the founders of Iona and their descendants - 1800 - 1850 by S.R. MacNeil.
Her parents were John D. "Blacksmith" MacNeil Piper's Cove and Mary Ann MacNeil, Grass Cove. Mary Ann's parents were James "Lieutenant" MacNeil and Mary Ann MacDougall from Christmas Island. Margaret was known as Maggie. Her siblings were James, Daniel, Maria, and Eliza.
Maggie's brother James married Lucy MacNeil from Gillis Point. Daniel married in the states but lived in Iona and later moved to the mainland. Marie married a Deveau from Little Bras d'Or. Eliza married John Young from Little Bras d'Or.
What is your grandmother's name and who did she marry? I will see if I can find her in the book.