O Sheikh, is it permissible for infidel women to perform ghusl after menstruation?!

It is permissible for a non-Muslim woman to perform ghusl (ritual bath) after menstruation. If she is a non-Muslim woman not married to a Muslim man, ghusl is not obligatory for her because her purification does not benefit her before embracing Islam. Even if it is said that disbelievers are addressed by the ancillary rulings of Sharia, they are not obligated to observe them while in a state of disbelief, nor are they commanded to make them up if they embrace Islam.

However, if the non-Muslim woman is married to a Muslim man, he has the right to compel her to perform ghusl after menstruation or postpartum bleeding, because it prevents intimacy. If she needs to purchase water, its cost is incumbent upon him, due to his right.

Ghusl in the sense of personal hygiene has no religious prohibition; therefore, it is permissible for a disbeliever to clean and wash herself.