"She is my grandmother."
Translation:ʻO ia koʻu tūtū wahine.
You are close with your alternative sentence. You just need to start it with 'O - ‘O ko‘u tūtū wahine ‘o ia. Your alternative is a more common word order in Tahitian grammar, but in Hawaiian ʻO ia koʻu tūtū wahine. is a bit more common. Both are correct, though.
I answered "He ko'u tūtū wahine 'o ia" and the program marked me wrong, but when I entered that same phrase into my online translator, it gave me back "She is my grandmother." Can someone explain to me (and apparently to the online translator) what is the fine difference here? And what nuance are we supposed to be picking up from this fine discrepancy. E kokua mai.
Twice - since the very next question I got was the same - at least they're consistent. As was I. Yep. Still "wrong."