Translation:How is your aunt in Osaka?
In this context, の seems to indicate 'in', the uncle is living in Osaka. If the aunt is from Osaka, it is possible to say おおさかのおばさん but I may say the aunt coming from Osaka おおさかからきている おばさん. Sorry i dont mean to complicate things but it is Japanese anyway :))
Auntie was used previously in the lesson. But here, they will not accept it.
So, if I understand the の particle correctly, it kind of means "of". That would make this sentence be constructed as something like "Your aunt of Osaka is well?" Does that sound right to people?
This somehow makes complete sense to me, because I used to address my grandmother using the place she is from as prefix before "grandma" in my native language.
Is the の part here to indicate where she currently lives, or where she was born?
の is the possessive particle. 私の車。(わたしのくるま) my car. i think it is also used as a hanging particle when forming a casual question too.... my grammar is kinda bad tho. 今、何知ってるの