Ovulation starts first or menstration in a girl life on first time?

By definition: Menstruation follows ovulation, so ovulation is first. However a girl may have bleeding that is not menstruation (breakthrough) before she ovulates.

Either: In pubescent girls the estrogen driving the changes can drive uterine tissue buildup that will eventually breakdown as menses, ovulation or not, and many don't ovulate on a regular basis for the first 6 mo or so. However, they could ovulate during the peak of estrogen driven buildup and have a normal period in response.My first delivery as a student was to a 13 yo who had never had a period.