I know you can find Mary M Conn nee Prewitt on Sparkythewonderdog's family tree.

Here is also the site to the Guion Miller Index application number for her to receive Native American Benefits, don't know if it was approved but the address you can copy and paste below and is on page #63 name: Conn, Mary M.

http://catalog.archives.gov/id/300330?q=*:*

Her app number is 35976

Hope that helps.