Is ghusl obligatory if menstruation begins immediately after intercourse?

A menstruating woman is not required to perform ghusl (ritual bath) for major ritual impurity (janabah) until her menstruation ceases. If she performs ghusl for janabah during her menstruation, her ghusl is valid, and the state of janabah is removed. However, the ruling of menstruation remains until the bleeding stops. If she postpones the ghusl for janabah until after menstruation, and she intends thereby both janabah and menstruation together, that is sufficient for her according to the majority of scholars. However, if she only intends one of them, it is not sufficient except for what she intended, due to the Prophet's (peace be upon him) saying: "And indeed, every person shall have what he intended."