I have a 5 mo old pit, Lady, she is around 20-25 lb (and growing more every day

) and loves to eat. I currently am feeding her Science Diet Puppy 1.5-2 cups, 3 times a day. But she is always hungry, always looking for food, she eats so fast. Should I be feeding her more?? I am following the instructions on the package but feel like I should feed her until she is full. PLEASE HELP ME AND MY HUNGRY PUPPY