According to the 1880 census, Matilda Ann gave her birthplace as South Carolina. She also gave the birthplace of both her parents as South Carolina.
http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=DE&GSfn=m&GSpartial=1&GSbyrel=all&GSdyrel=all&GSst=46&GScntry=4&GSob=n&GSsr=3921&GRid=23464611&df=all&

The 1850 census of western Choctaw County reports next door neighbors of James Monroe and Matilda Ann Deskins to be Jesse and Elizabeth Peoples, (ages 49 and 45, respectively). These are probably her parents, both born in South Carolina. The household of Jesse Peoples (or Peebles/Peeples) can be found in Fayette County AL in 1840, and Barnwell District SC in 1830. Evidently the Peoples (or Peebles) moved to Alabama about 1831, and then to Mississippi about 1845.

If tracing someone in the Peoples family to a native American is your goal, then explore records of Barnwell District SC. The family had only been in Mississippi a short time prior to 1850.