Since no one seems to bat an eye or mention Fatima's pointed ears, perhaps they aren't as uncommon as one may think. While no one else has such ears, it seems that people with Shadow Frost magic are also uncommon. Witches and Wizards are apparently just humans with high aptitudes for magic, but it also seems that this ability to use magic somewhat changes a person's physiology. It has been stated in the game that magic aptitude is genetic. This is stretching it, but since the ability to use magic is genetic and thus a mage's body chemistry is different from that of normal people, then perhaps the powers of Shadow Frost outwardly changes its users a little, such as making their ears pointed. Or the genes for Shadow Frost magic are linked to the genes for pointy ears. It also fits with users