This is years after your original question, but I'll post this for you, or anyone doing similar research.I'd be very interested in what every you could share on Mary.
As far as your question on a census, she and 'Osaforus Standlee' are family 408 at the bottom of the page in the 1850 census for Prairie Township, Carroll County. On the next page is their daughter Hannah (now married to William Pyle). The H/H for Mary continues, and the first name prior to the Pyles is Susanah, another daughter still living with them. After the Pyles are various Standlee households, and a coupe of Davis households.The household of Jefferson Davis, and wife Catherine, is the Granddaughter of Mary, through her son John Standlee.(The household of Aaron Davis is Jefferson's brother.)