Adrenals, thyroid. Weight around stomach responds to adrenal reset and weight around thigh is a sign of ineffective thyroid.
Some exercises help. To help the tummy look flatter, one can do exercises to build very strong abdominal muscles. It will take a lot of work, and will burn off calories. One must not eat more calories than she burns off, or she cannot lose weight. Helpful weight loss foods are natural foods that take time to chew but contain few calories. Many teens are still growing, and may not need to lose weight (they get taller).