What's the healthy weight for an 16 yr old girl who's 5'1?

100-125#: would be in the healthy weight zone for a girl 5'1", but other factors to consider are level of maturity and muscle mass. Most important is getting regular exercise and rest, eating a healthy diet, and feeling good about yourself. If you are above that, then eating just 100-200 calories less a day will let you lose 1-2 pounds a month, which is safe way to manage overweight or reverse to gain.

A healthy weight: is one that keeps your BMI between 18 and 24, that is associated with normal menstrual cycles and a normal level of physical activity, and that is maintained by a healthy diet.