I didn't find Rena's birth info in Ancestry nor in FamilySearch. You need to search for her birth info in Oklahoma.
I found a family tree which shows her father as:
William irvin McDowell
Born: 1875 Pulaski Co. MO
Jeannette Dov Hulsey, b. 1882, Franklin Co. AR (her mother)
In 1910 Rena and her siblings with living with their Hulsey grandparents in Bald Hill, Okmulgee Co. OK and they're listed as white on the Census. However I don't think you reliably base race on that column in the Census. Successful Searching!