Died: 20 April 1926, Marshall Co. per death cert #103682.
Source: South Dakota Death Index 1905-1955.
I looked in findagrave and the State Historical Society's grave index, http://apps.sd.gov/applications/DT58Cemetery/
but didn't find her.
Her burial place might be in/on her obituary and should be on her death certificate. I don't know where to find her obituaries unless you do a Google search for Marshall County South Dakota Public Library and contact them.
You can order a copy of her death certificate from South Dakota Dept. Health, http://doh.sd.gov/VitalRecords/genealogy.aspx
but I can't guarantee the field will be filled in. Successful Searching!