What is the right weight for a 13 year old girl?

Well there are certain stats out there, but you need to keep in mind that everyone has different amounts of muscle and fat, and muscle weighs 2.94 times as much as fat, and since people come in all different shapes and sizes, there's no way to say for sure how much fat and muscle you should have exactly. Not to mention people are all different heights, and the taller you are, the more of you there is, the more you're going to weigh.
This might help, but remember, these numbers aren't exact, it's just to give you an idea:
http://www.disabled-world.com/artman/publish/height_weight.shtml

it depends on how tall you r like im 13 and I way 80 something but im very tall unlike other 13 year olds and I dont really look fat