Researching My Family Ancestry Blackbull

I need help finding my family line,
mother: Twila Marie Olson Salazar
Grandmother: Arlene Marie Blackbull Olson
GG: Mercy Marie Blackbull Killsplenty
GGG: Elizabeth Dorothy Blackbull, possibly Buckman

My grandmother started with the history of our family, but passed away before we got further. I believe somehow we were related to Chief Blackbull of South Dakota, I can't find any information other then what I already have, can you Help?