It depends on how many calories they consume; if you are of a slighter build and eat less calories, you need to burn less.
Maintain a 2000 calorie diet.
2000 calories per day
You need to burn more calories throughout the day than you end up intaking.
A 10 year old girl will need approximately 1,400 to 2,000 calories per day.
About 1,600 to 1,800 calories a day, with healthy choices and exercise.
Generally about 1,800-2,200.
You would need to lose 3500 Calories to lose 1poundDecrease your daily calories by 30%.
About 1,600 calories a day.
Adults should get 2,000. Children should get 2,500.
This depends on whether she is still growing or not. Some girls have stopped growing very early on and will need less calories to keep their body weight the same. If they would still be growing, they would need more calories to help their bodies. For a 16 year old girl that is still growing, I'd recommend 2500 calories a day. If not growing, 2000 calories would be enough, as recommended for women in general.
You can't lose weight by guessing. You will need to know how many calories you need per day by the amount of exercise you do. The average person burns 2000 calories per day. In order to maintain homeostasis within the body, your intake of calories should match how many calories you burn.