I cannot believe I found your post. Greenberry O'Daniel is my Great, Great, Great Grandfather! I have been searching for his cemetery for a couple of years now. I live in far western Ky and have been able to find his son's grave but never his. Now I know why. James Louis O'Daniel, who was Greenberry's son is my Great Great Grandfather. He was married to Eliza Ann Burgess (Clark) O'Daniel. James' and Eliza's burial sites are very close to where I live.
If I read your post right, you were wondering about Mattie Burgess and whether or not she was Cherokee. According to my findings, Mattie was actually the twin sister of my Great Great Grandmother, Eliza. I haven't come across any information to suggest they were of Cherokee descent, but I will check into it.
Glad I found your post. I hope we can share further information. We are actually hoping to have an O'Daniel reunion this fall to share information and pictures...I can't wait!!!