The age range for a girl's first menstrual period is usually in10-15 years oldBetween. This age range is not absolute, and the rate of physiological development and the timing of menarche vary from girl to girl. Some girls may have an early or late period within this age range, and this is normal.
If a girl's menarche age is too different from the age range of most girls, or does not match the rate of their physiological development, then parents need to be vigilant. This could mean that the girl has certain health problems and needs to seek help from a doctor.
Here are some of the factors that can cause a girl's menarche age to be out of the normal range:
Physiological factors: The speed of physiological development and the time of menarche in girls may be affected by various factors such as genetics, endocrine, and organ development. If a girl's age at menarche is not much different from the normal range and there are no other unusual symptoms, there is usually no need to be too worried.
Malnutrition: Malnutrition can lead to stunted growth of the female body, which can affect the timing of menarche. Parents should take care to ensure that their girls' nutritional intake is balanced and avoid overeating or picky eating. 
Diseases: Some diseases such as endocrine disorders, dysplasia, etc., may cause the age of menarche in girls to be earlier or delayed. If the age of menarche in girls is quite different from the normal range, and it is accompanied by other abnormal symptoms, such as obesity, hirsutism, breast dysplasia, etc., it is recommended to seek medical attention in time.
The age at menarche in girls is not absolute, and the speed and timing of physical development varies from girl to girl. If a girl's menarche age is too different from the normal range, or does not correspond to the rate of their physiological development, then parents need to be vigilant and seek medical help in time. Parents should also pay attention to girls' mental health and help them face physiological changes and challenges in their upbringing.
To help girls better cope with physiological changes and growth challenges, here are some suggestions:
Pay attention to mental health: Parents should pay attention to girls' emotional changes and mental health conditions to help them face physiological changes and challenges in their growth. For example, books and articles about puberty can be read with girls to learn more about physical and mental health.
Establish good communication: Parents should actively communicate well with girls, strive to understand their inner thoughts and feelings, and encourage them to express their emotions and needs. This can help girls better cope with physiological changes and challenges as they grow. 
Provide the necessary support: Parents should provide the necessary support and encouragement to girls as they face physiological changes and challenges to their growth. For example, when a girl is facing menstrual problems, the necessary help and comfort can be provided to make her feel no longer alone and afraid.
Develop self-confidence and self-awareness: Parents should help girls develop self-confidence and self-awareness, so that they understand their physical and emotional needs and learn to protect their rights and dignity. This can help girls better cope with physiological changes and challenges as they grow. 
A girl's age at menarche is not the only measure of her health and growth. Parents should pay attention to the physical and mental health of girls and provide the necessary support and encouragement to help them face the physiological changes and challenges of growing up. Parents should also respect girls' individual differences and needs, so that they are fully cared for and supported as they grow up.