It mostly starts during adolescent where girls start experiencing changes in their bodies and emotional changes rise and they start feeling attracted to the opposite sex. A good, learned parent will understand this and will try hard to help their girls control this.In case of a don't care parent, thats where the girls do mess up since they're not guided. In some girls, the always start messing in their late teenage period when they're almost becoming youths. This is due to hormones functioning differently in different people. Thanks to education system, the adolescent stage is always tackled in one of the subjects.