Childhood Obesity: Healthy Child Weight
The very best way to know the optimal weight for your daughter is to have the doctor or another health professional calculate her body mass index (BMI), which will tell you the best weight for her age and height. (You can also calculate her BMI online, using tools from the CDC.)
BMI calculations are still somewhat of an estimate, because a more muscular child will weigh more than one who is less muscular. But it is a good gauge. For a good rough estimate for teenage girls, you can calculate 100 pounds for 5 feet and 5 pounds for each inch over that.
If you're concerned about your daughter's weight, talk to her doctor, who can give you additional guidance.