What is the ruling of Islamic law and the expiation for one who feigned prayer while menstruating out of shyness to inform others of her menstruation?

It is not permissible to feign prayer during menstruation, and there is no fault or embarrassment in its presence, as it is something Allah has decreed for women. The mother should have excused her daughter and taught her gently, without shouting or scolding. It is sufficient to teach her how to act in the future. As for what has passed, let her seek Allah's forgiveness if there was any sin in it; there is no expiation required of her.