@alessaaa Idk about most girls, but by the time I was 11, I was already wearing a B cup bra. I though it’s pretty normal since many of my friends did so as well. Normally breast will develop within 1-2 years after menstruation. Many girls start menstruation around 9-10 years old. After I google it up, it’s actually a pretty common situation. 50 years ago, girls hit puberty around 14-15 years old. But nowadays, because people eat more than enough nutrition, they have puberty earlier than before. So, if you are a parent, be prepared because kids nowadays develop faster. My younger cousin is a girl and when she was 13 years old, her height is already 1.75 m. So she totally looked like a college student.
Btw, it truly is strange why this issue becomes your focus.