I too am researching Francis (Mackleroy) Shaw who was married to John Baptist Shaw. I am based out of San Diego and the "Shaw's" were my 5th great grand parents on my father's side. By the way it appears that the proper spelling of her maiden name is Mackleroy as I have a copy of Achibald Mackleroy's will dated 1760. And his name on the will is spelled Mackleroy.
I just obtained a copy of John Baptist Shaw's will here in Raleigh, North Carolina at the State Archives and will be scanning it and posting it to my family tree upon my return to San Diego.
I am very interesting in your theory that Frances died after the 1850 US Census. I have questioned the date of her death as reported by so many here in ancestry around 1816. I would love to talk to you and compare notes if that is at all possible.