Blackfoot Tribe, Cherokee Tribe - Hadley Family

Hi, I am not sure where to begin so I hope what I am about to ask is understandable. My name is Patti Harris. I am doing some family research history. I know my mother was Cherokee and Blackfoot Indian. Her name was Mary Landers at time of death. I was wondering if you may have any information requarding her mother who's name was Dorthy Hadley at time of death. They didn't live on the land that I know of. I need some help in finding out if grandmother Dorthy was full blooded. If there is any way or any information that can be shared with me I would be greatly apperciated. Thanks, Patti