Yes, when a girl is bleeding, it is most likely that she is on her period.
Menstruation, often called a "period," is a woman's monthly bleeding. According to provided references, it's the process where the body discards the monthly buildup of the lining of the uterus. Menstrual blood and tissue flow from the uterus, through the cervix, and out of the body through the vagina.
Therefore, bleeding from the vagina in a girl is generally indicative of menstruation.
