>>76254035
I'm guessing the cousin is in a similar age group of the original posts OP because she compares herself to her cousin. So let's say +-5 years. If the person is the cousin's mother, chances are they are married to the uncle or at least common law. In that case, still just say Aunt.
These tumbler posts have a habit of othering people they don't like by distancing their relationship to them.