Is 90 pounds at age 12 normal?

In my opinion she is not that far off the "normal" scale for a girl of her age. I am 5'2 and weigh 108-114 depending on the time of yr. I also was a bodybuilder that competeted. I am thin but very muscular. Most think I am 100 soaking wet. I get a little---no, very irritated by their comments, because they usually come from someone that is obese. She may be 10-15 lbs underweight. I recall a chart --5'0=100lbs and 5lbs for every inch ex 5'4=120 that may be for an adult in a totally different age range. Check her BMI(body mass index) and have her body fat% taken and go from there.