My mother is a non-Muslim who belongs to the People of the Book (a Christian or a Jew). Is it permissible for my wife to remove her head cover before her? What is a woman permitted to see of another woman's ‘Awrah (body parts that must be covered)?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The ‘Awrah of a Muslim woman before other Muslim women is the same as the ‘Awrah of a man before other men. So, it is allowed for a woman to see another's whole body except the area between the navel and the knee.

The ‘Awrah of a Muslim woman before a non-Muslim woman includes all her body except what is often revealed thereof during housework, such as the face and the palms. It is also said that the ruling remains the same whether the woman is a Muslim or a Thimmi (a non-Muslim living in an Islamic state) and this is the preponderant opinion.  

Allaah Knows best.