I found your post through a Google search and wondered if we might share information. I have found an ancestor line for Mahala (mehala) Hubbard which might be your ancestor as well as mine.
Here's what I know for sure:
I know my great grandmother was Pearl Ruth Farmer and she was part Cherokee and married to Thurmond Harris. She was born in Kentucky in 1897.
I believe Pearl's mother was Martha Caroline Pharris and her father was Crawford Lee Farmer.
I believe Martha's mother was Jane Millie Graves
I believe Jane's parents were Adam Graves and Mahala Hubbard. Your post suggests Joseph Latham Graves was Mahala's husband
I'm not sure if the Cherokee blood came from Martha or Crawford's line but I've traced Crawford's line back numerous generations and have concluded the Cherokee line must come through Martha.
I believe Jane Millie Graves was married to Archibald Farmer but he was not Martha's father. I haven't been able to find a marriage or father listed for Martha.
My family lived in Tennessee, Arkansas, Oklahoma, Kentucky and eventually Indiana
Any information you might have I would welcome and I would be glad to share what I have. Most of the information I have found has not been verified except through Google searches.
Terry Harris Bradley