Unless she is a big-boned girl a 19.2 BMI for a 9 year-old girl might be a bit high; but I think think 66 lbs for a 9 year-old is not unreasonable.
Just for the record, I think BMI numbers can be completely irrelevant in many cases, especially for athletes.
From the picture she looks like she should gain a little weight. Certainly not overweight.
BMI, or any effort to use a simple formula to determine health is stupid and inaccurate.
When I was in the air force they started using a bike test measuring heart rate. It was supposed to measure how efficiently your body used oxygen. We had to take it at our assigned station. I was stationed at Cheyenne Mountain (NORAD) at an elevation of 9,564 feet. They claimed there was no difference between this elevation and taking it at sea level which is what the metrics were designed. Our significantly higher failure rate was simply due to our laziness.
She is on the low end of the normal BMI (which is a crap measurement) but nowhere near a high BMI.
Ill say. My daughter is a ballerina. All muscle very little fat. Wears a size 2. Last time she went to Dr (she is a full grown adult now) she was told her BMI was a bit high!!!!
I wish I could wear a size 2 and dance the way she does.... BMI breaks down on both ends of the scale. You have to use common sense.