Dear Ms. Boren,
Thank you for posting your request on History Hub!
For an overview on how to begin your research, we suggest that you review NARA’s Native American Heritage as well as the FamilySearch Research wiki for Indigenous Peoples of the United States Genealogy. We also suggest that you search the various Free US Indian Census Rolls 1885-1940 that are organized by Tribal Nation for mention of your great grandmother.
When embarking on Native American genealogy, please note that the records in the custody of NARA often only detail those living on the reservations or being administered by the Bureau of Indian Affairs. If an ancestor was native yet left the reservation, they will not be recorded in NARA’s records and tracing their genealogy may be difficult.
We hope this is helpful. Best of luck with your family research!