a lot of white Americans have some black and/or Indian ancestry and black Americans often have some white and/or Indian ancestry.
The US, especially in the frontier, was never as racially homogenous as made out to be.
It appears that her parents took good care of their child and she had a pleasant childhood with two parents.
Also note, that like most here on FR, her blood is red.
My wife had a dna search done one her and found she had a black ancestor who lived in England sometime in the last 500 years. My wife looks like a typical white person. It would be interesting to see the results of a dna test on many people.