Delvo
Дэлво Δε&#
Both parents were mixed, not black. Both babies were mixed, not white or black. The lighter-colored one wasn't "snow white" and still had a mix of traits. To the limited extent to which her skin was lighter than those of her parents or sister, it just means that she inherited a few genes from her two white grandparents (one through her mother and one through her father) instead of her two black ones.Remember the twins born in England, of black parents, yet one was snow white? No dominance of either meaning there.
Mendelian dominance & recessiveness might apply to some of the genes that affect skin color, but not to all, and not necessarily even with the one that results in a darker phenotype being dominant. (It could be the other way around.) Since human skin color, in phenotype, is a pretty simple matter of how much melanin there is, or at least how much of each of two kinds of melanin there is (one yellower and one redder), and the amount of any compound is variable along a spectrum from low numbers to high numbers, it's quite likely that most or all human skin color genes have non-Mendelian results, so, all else being equal, a heterozygous state for any given one of those genes would yield an amount somewhere between the two possible homozygous states. But I don't think the answer is even known at all in most cases yet. For that matter, some of the genes affecting skin color might not even have been identified at all yet.