Imaam Al-Qurtubee said in his famous tafseer:
“His statement “their women” refers to the Muslim women (1). The polytheist women, such as the disbelievers and their types are exempt from this. It is not permissible for a believing woman to uncover any part of her body in the presence of a disbelieving woman, unless she is her slave/servant.
Some scholars considered it detestable for a Muslim woman to host a Christian woman or have her ‘awrah looked at by her.
‘Umar Ibn Al-Khattaab once wrote a letter to Aboo ‘Ubaydah Ibn Al-Jarraah saying:
‘It has reached me that the Muslim women enter the public wash areas along with the disbelieving women. So prevent this and do not allow it, for indeed it is not permissible for a disbelieving woman to see a Muslim woman uncovered.’
So Aboo ‘Ubaydah stood up at that and called out saying:
‘Whichever woman enters the public bath areas without an excuse, not wanting except to purify her face, then may Allaah darken her face on the day when the faces will be whitened (purified).’ “
[Tafseer Al-Qurtubee, 12/233]
(1) This is based on the saying of Allaah: “…And (tell them) not to reveal their zeenah (adornment) except to their husbands, their fathers… their women…” [Soorah Noor: 30-31]