>>45767811She's a kid, she just talks in a sophisticated manner due to always being around her grandparents (remember that Hapu and her family are the only people that actually live on Poni Island, not counting the Seafolk Village).
>>45767909She only becomes the new Kahuna due to the death of her grandfather, the previous one. Also, the Tapu pick the Kahunas and Tapu Fini presumably thought Hapu was the best candidate (not that there were many choices.)
