Yáʼátʼééh! The word for “my paternal uncle” is formed by shizhéʼé + yázhí. And shibízhí is for “my paternal aunt”. I really do not know if a word for an unknown, or non-related “auntie” is used in Navajo. If the person is from an unknown origin or clan, then I think only “a woman” can be used. Still, there would be a polite form to mention ’all the maternal aunts”, and “all the paternal aunts” in a discourse, or some dialogue. But these forms are not still covered in the course.

Here are some audios for the Navajo Kinship.

https://forum.duolingo.com/comment/29367017

I hope it helps. :)