Yáʼátʼééh! Of course yes. I have reported all the errors here. The hints are wrong, the Navajo sentence is wrong, the "Correct sentence" is wrong, and "My answer should be accepted":
My maternal grandmother has an older sister.
Note: the Navajo word ádí cannot be used as a possession. Here, the possessed form is bádí. And, Navajo actually uses a possessed form for the subject and the object here, then, the English would literally be "My maternal grandmother has her older sister / bádí."