Must a girl who wears the hijab cover her feet, and is it permissible for her to wear an open-toed shoe (sandal) with socks that cover her feet?

In the era of the Prophet, peace and blessings be upon him, women were keen to cover their feet, and they used to lengthen the hems of their garments by a shibr (span). When it was said to them, "Then their feet will be uncovered," the Prophet, peace and blessings be upon him, commanded them to lengthen the hem by an dhira' (cubit). Therefore, it is not permissible for a woman to wear open-toed shoes that expose her feet; rather, they must be covered either by a covering garment or by socks.