Whats a good way for teenaged girls to get muscles and abs and butt?

Diet & exercise. To get "definition" or "cut" where the muscles are visible it takes work and diet. Most girls who attain this appearance have a body fat content of 5-7% or 10% at the most while the average teen runs 15-20%. Getting down to that level of minimal body fat requires a low carb high protein existence along with regular workouts.