Is it necessary to perform ghusl for janabah if menstruation occurs afterward?

If a woman experiences janabah (major ritual impurity requiring ghusl) and then her menstruation begins before she performs ghusl, she is not required to perform ghusl until she becomes pure from menstruation. Then, she should perform a single ghusl for both janabah and menstruation. This is the view held by Al-Shafi'i and Ibn Qudamah. However, if she were to perform ghusl while menstruating, her state of janabah would be lifted according to some scholars.