I don't think Pickett was her maiden name. She appears to have married a man named Pickett in between 1870 & 1877, because they refer to her as "Mrs." Mariah Pickett:

Source Information:
Hunting For Bears, comp. Mississippi Marriages, 1776-1935 [database online]. Provo, Utah: MyFamily.com, Inc., 2004. Original data: Mississippi marriage information taken from county courthouse records. Many of these records were extracted from copies of the original records in microfilm, microfiche, or book format, located at the Family History Library.

Mississippi Marriages, 1776-1935
Name: Mrs. Mariah Pickett
Spouse: Allen Buie
Marriage Date: 22 Feb 1877
County: Jefferson

She may have died between 1880 & 1883, unless there was another Allen Buie.

Mississippi Marriages, 1776-1935
Name: Allen Buie
Spouse: Chatty Wood
Marriage Date: 24 Aug 1883
County: Jefferson