Realistically i think both parents have to have the same mix for it to also apply to her. For exampleWhat?
if both parents are half Irish and Half Nigerian, then she would also be half Irish and half Nigerian. But if one is half Nigerian half Russian, and another is half Japanese and Half Kenyan. That's 4 halves, that doesn't equal to biracial, just mixed race. Thing is everybody is mixed race, you can pull up and ancestry report of anyone and find 4 or more races in your own back round that make up a majority.