All perfect praise be to Allah, The Lord of the Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
A woman's foot (Lower leg] is part of her Awra (Parts of the body that must be concealed during prayer) that must be covered while praying and in the presence of Non-Mahrams according to the majority of Muslim jurists, since Umm Salamah said that she asked the prophet (PBUH): "Can a woman pray in a shirt and veil without wearing a lower garment? He replied: "if the shirt is ample and covers the surface of her feet. [Abu Dawood 640]. However, there is disagreement among the scholars of Hadith whether this Hadith is Murfoo' [ Discontinued Hadith) or Muoqoof [Hadith traceable to the Prophet].
Moreover, according to Hanaffi scholars, woman's foot isn't considered part of her Awra while performing prayer since it is stated in [Al-Hidaia vol.1/pp.259] :" Woman's foot isn't considered of her Awra."
However, the majority of Muslim scholars stated that a woman is not permitted to get out of her house without wearing socks and her prayer isn't valid if part of her foot is uncovered. And Allah Knows Best.