Congratulations, your daughter is getting first signs of puberty - breast buds. These are something like small mounds on the nipple - usually your daughter may complain about soreness or tenderness - its all normal. It is also likely that one breast starts before the other. It is also likely that one breast grows a little larger than the other, in about a years time, they usually level out. She may also show signs of pubic hair growth - its all a process of being a mature adult woman
Yes it is. My female friends and I developed our breasts at age 9 and some of them at age 8. It was considered too young and too early in my younger days but more of it is happening now a days and has been since the 1980s. My sympathy to you and your daughter. I hope she can adjust to it.