Final answer:
A girl will get her first period in the later stages of puberty when the growth spurt is waning and the other changes are well underway.
Step-by-step explanation:
Typically, a girl will get her first period in the later stages of puberty when the growth spurt is waning and the other changes are well underway. This usually happens around the ages of 9 to 11, which is when the growth spurt begins. The development of breasts usually occurs before the first menstrual period, so it is not a direct indicator of when the period will start.