Is a single ghusl sufficient for purification and for a woman to enter Islam if she embraced Islam while menstruating or shortly after her menstruation ceased?

What is incumbent upon you is to ignore the whispers and not pay attention to them, for your Islam remains valid merely by doubt, and you do not become an apostate unless you commit that which necessitates apostasy. The preponderant opinion is that disbelief does not necessitate ghusl (ritual bath), and whoever embraces Islam—whether an original disbeliever or an apostate—is not required to perform ghusl unless they committed, while in their state of disbelief, something that necessitates ghusl (such as menstruation or seminal impurity). The ghusl in such a case would be for that reason and not for embracing Islam. A single ghusl suffices for multiple events.