Starting Sept. 5, 2014, Genealogy.com will be making a big change. GenForum
message boards, Family Tree Maker homepages, and the most popular articles
will be preserved in a read-only format, while several other features will
no longer be available, including member subscriptions and the Shop.
This is a few years later, to your question, "Where are they in 1850?". If you have not found this yet, Mary Sina Frazier was the daughter of William Frazier. In 1850, she is still at home in Vermillion County, Indiana. Listed as wife of William is Elizabeth, but that is not to say she is mother to Mary Sina. You might look for William Daffron in that area. I wonder why they would marry in Illinois?
Also in the Frazier household is Mary Sina's sister Jenette, who would marry John Hendrickson. Both of these couples, along with William Frazier, would migrate to Missouri -- Benton County and Dallas County.
I am looking for more information on Mary Sina, specifically when she died.