Until menses. Girls grow until menses, once menses starts, growth rates taper and cease over that next year. This can certainly vary on the timing, but on average menses starts in the US population at age 12. Growth at age 21 would be very unusual!
Myth. Most girls stop at 15-17, or about 2.5 inches after their first menses. The open growth centers of the long bones permit continued linear growth.The hormones that bring on the start of menses begin signaling the growth centers to close. An x-ray of the wrist and hand can determine whether additional growth is possible.When the growth centers close, linear growth stops.
Growth. Most girls grow until they get their periods and then once they start mense, they usually only grow another 2-3 inches.