Menstruation is controlled by hormonal changes in the body, and these changes happen naturally over time. The average age for a girl to start menstruating is around 12 years old, but it can happen anytime between the ages of 8 and 15.
It's important to remember that every girl's body is different and that there is no "normal" age for starting menstruation. If you are concerned about your menstrual cycle, or if you experience any unusual symptoms or changes in your period, you should speak with a healthcare professional who can provide you with personalized advice and guidance.