How much weight does a 16 year old female should be?

This depends on how tall you are, and your level of physical activity. Find you BMI (dependant on age, height, and weight) and go from there. This calculator will tell you whether you are overweight, average (good), or underweight, based on those factors. It may not be accurate if you do tons of working out. http://www.nhlbisupport.com/bmi/