This is an interesting position to be in. I don’t quite know what to make of Dolemite’s post, as one’s ancestors is not a term clearly defined.
Family is family where I come from, and my (adopted) cousins are my cousins, we share the same grandmother, their respective (adoptive) moms are my aunts, my mom is their aunt, and when we were kids were we to step out of line, we’d all get our butts beat for the same transgression by the same hand.
So, ancestry is more than blood line for me. And in that case, if my ancestor originated from one of the recognized countries on Dolemite’s list, I would go forward with the designation.
I do see where the waters get murky in terms of definition. Can you tell us if your sibling encountered any pushback from her school offices? Any inquiry after the disclosure was made on forms when applying/matriculating?
As for identity, I’ve been working on being clear with my own child who does not have a chance of being identified as Black any more than Boomer Esiason does (though I am Black), that as his consciousness of self is Black-centered, it does not matter that others will question him.
As @BUalum93 says, “The key word being identify.”