Why is she so tall if she grew up with little nutrition and with short parents?

My 15-year-old cousin in a developing country is 5'7''. For reference, her 25-year-old brother is 5'4'', same as her dad, and her mom is 4'11''. Growing up in a poor household, her mom (my aunt) didn't have enough money to buy milk for her when she was little. She rarely eats veggies or meat because her family can't afford it; she practically grew up eating rice and eggs. I remember when she was 8 or 9, she was really short. Now completely different. Her older brother grew up on basically the same thing, and he's 10 years older than her but 5'4''.
Why is she so tall if she grew up with little nutrition and with short parents?
Post Opinion