I was a little sad too and my DD was 14 when she started. I didn't want my "little girl" having to deal with pads, tampons, hormonal zits, cramps, mood swings, ect. It's not too thrilling having to deal with them by proxy either lol. It was all just poignant I suppose.
On average, girls grow about 2 inches after starting their periods. This is just an average meaning some will grow more, some will grow less. My DD fits in this. She was actually small until about 12. Then she sprouted many inches and started to develop. Then her period hit and she's only grown about 2 inches since and only 1/2 an inch in the last year. She's 5'8" and happy at this height. My two nieces were still growing at 18 (one is 6', the other 6'2") but their parents are both huge so really, no surprise. I don't know the statistics on girls who start very early but the girls we know who started at 10 or 11 had already amassed most of their height.