For children who are entering the adolescence stage, especially for girl they are generally become more curious and aware about themselves. Some girls are physically developing faster than any other girls, such as the growth of breast, private hair and menstrual cycle. This normally happens around the age of 11-13 year old. There are many cases that they start having period at 9 year old, and there are also cases for late bloomer that do not have their period until the age of 15.
But usually their state of minds or mentally will become more aware at the age of 11-13 year old, where they will have many curiosity in their mind. At this age they become more aware about their surrounding and reality and trying to separate between fact and fiction. As their parents, it is our jobs to provide them with the right information to help and protect them from false and misguided information.
Providing the right information
Unfortunately there are many girls that reluctant to discuss this matter to their parents. This is usually because they are afraid, embarrassed and shy to talk and fulfill their curiosity. This behavior is a common thing; even they have open communication relationship with their parents. They often feel uncomfortable, inappropriate or even “gross or dirty” to discuss about sexuality with their respected parents. Therefore they prefer to seek the information by themselves to satisfy their curiosity.
It would be wise if their parent do not force their girl to communicate openly about this matter. It can resulting that they become more closed up and distances themselves with their parents. But you can start discuss this private matter at their early adolescence stage around the age of 9 little by little. This will make them become more comfortable to talk and discuss this matter with their parents.
You can also provide other source of information such as book or website that provide proper information, and then discuss it together. If you think you cannot provide proper explanation yourself, then you can ask the help from someone you can trust to explain it to your girl such as doctor or other adults from family or friends and satisfy their curiosity.