A wonderful mom told me she felt so badly that her daughter got such a late start pitching and was always playing catch-up. She began pitching at 10-years-old. That is not late! I told her about working with an athlete who started pitching at 14, eventually taking her team deep into the College World Series as a freshman.
It has nothing to do with when you start. We have over 100 Certified Instructors who have produced several hundred D1 pitchers in the last ten years. There is no correlation between when she starts and how she finishes. None! In fact, quite the opposite. Yes, we like them to begin by mid-teens, but even that is not a rule.
Starting too early carries several risks. One is burnout. She may not be mature enough to deal with the emotions that come with pitching. Just because someone else handled it fine does not mean it is right for every girl. You are pitching in heat and cold, mounds with holes in front of them, inconsistent umpires are frequent at younger ages, and your parents just “spent a boatload-of money to bring you to this tournament so you could embarrass us.” We hear these stories daily. A surprising number of kids put the ball down and find something else that has less pressure.
Her body may not be ready yet. I did not want either of our daughters to begin until 10-years-old, though the younger one pushed me a year earlier. Both went to pitch D1. Back to my point, not everyone matures at the same rate. She needs substantial body awareness. Get her in the field, teach her to run and hit, and then we can teach her the similarities in running, hitting, throwing and pitching. Let her come when she is ready.
Finally, when she begins is far less important than what she is taught, If you bring me a student who has been coached into mechanical, stiff moves for 3 years, we are far worse than if we had started from scratch. They often come to us injured, frustrated, and want to know why all of the newer pitchers are blowing past them.
Do not be in a hurry. Be sure she really wants it, let her work for it, and maybe she will feel a little more invested. Then, absolutely make sure that she is coached right. Do it right the first time because you make our jobs much harder when she comes to us beaten down and confused.