Must a woman who suffers from a menstrual disorder and whose bleeding has continued for longer than her usual period due to a hormonal imbalance perform ghusl and prayer, or should she wait for the bleeding to stop?

The maximum duration of menstruation is fifteen days. If the bleeding period exceeds a woman's known habit, the excess is considered menstruation, as long as the total duration of bleeding from its first appearance does not exceed fifteen days. If the bleeding period exceeds fifteen days, then it becomes clear that you are experiencing istihada (non-menstrual vaginal bleeding), and in that case, you should do what a woman experiencing istihada does.