She's Black and she knows it.
Her White mother probably got pregnant by a Black man back in the taboo days when she lied and told her racist White parents that she got pregnant by her White boyfriend knowing full well the father wasn't white, but Black and the very day she was born (mid wive(s) or local hospital) and after the total anger and shock of her father, mother and relatives wore off, she was immediately given away via adoption to her Black step parents.
When I was doing my family tree research several years ago, I found out that many birth certificates were incomplete and noted wrong because many black baby births during Jim Crow were done by Black mid wives who traveled throughout the neighborhood and not birthed in the local hospital.
Those mid wives, many who could barely read, write or count that well and were supposed to turn in all their birth records to the town court house, didn't keep good records and got paper work all mixed up, misspelled baby names on different paperwork among different families and also didn't check the correct boxes for race.
Also consider that the local racist Whites at the court house could give a good damn about the birth records of new born Black babies,
One of my aunts who was birthed by a mid wife that currently lives in Baltimore, MD, who needed her birth certificate for some reason and she had to travel back home to obtain it, found out her original birth certificate didn't have the actual date written on it when she was born.
The date of birth she always used was the written birth date that was written down in our family Bible for each family member birth that also includes a lock of your baby hair.
Also remember decades ago my aunts telling old stories when they were teenagers of young girls in the neighborhood getting pregnant, having babies out of wedlock and other older women of the neighborhood in their mid to late 20's, 30's and 40's wanting them (approval granted by the teenager's mother and father) to just give them their newborns to raise and call their very own because (1) husband died and lived alone (2) they could not have children and (2) because they though it would not be a real problem because the girl's family was already "too big."
Many of those women wanting other people's Black babies were the White women who were the granddaughters of their slave owning ancestors and that Black family (slave ancestors) who were all related due to slavery and who all lived only a few yards away or a few miles apart from each other.