I have been working on a narrative of the life of Simeon Adams Dunn just to cement in my mind what we have learned. I realized I really don't know the story of his second wife, Margaret Snyder. I have put out some inquiries and stared some research.
From what I can gather, she must have joined the church with her brother, Robert Anderson Snyder, and come to Nauvoo with him. Robert Snyder appears to have lived in close proximity to Simeon Dunn. I assume he got to know the family, and thus Margaret, in this way.
The image is the Hancock County Deed index, shows both Simeon Dunn and Robert Snider, their block and lot, and reference to deed book.