What is the average weight of a 5'7 teenage girl?

I disagree with the persons comment before.

The healthy weight range for a 5ft 7 inch girl is between 9 stone 2lbs and 11 stone 6 pounds

so that's 128- 160.

That's the healthy BMI weight of betweenm 20-25.

Any lower is considered obverweight and above is considered overweight/unhealthy.
The average weight is about 117-140 pounds, really it all depends on your bone structure, so if you have a small frame, you might be around 115-125, if your medium 125-135, and if you have a large frame you might be around 135-145. But if you really want to know your at a healthy weight just figure out your BMI, which you can do by just typing "BMI calculator" on google or something.