She would be your great aunt.
Your great uncle's niece could be your mother, or your aunt. It is also possible that she is not related to you at all, as you might not share a common ancestor.
cousin
Cousin. Your parents brothers and sisters are aunts and uncles. and the aunt and uncles children are your cousins.
uncles aunts sholud both spend an equal amout of time together depending on their relationship
Dursley
Your aunt is your child's Great Aunt, so your child is her great niece or great nephew.
You are their aunt or aunt by marriage.
The sister of your uncle is typically referred to as your aunt. If she is the sister of your uncle by marriage, she is still considered your aunt by that relationship. If she is your uncle's biological sister, she is also your aunt. In some cultures, the term "aunt" can be used more broadly to refer to close family friends as well.
You are not related to your uncles wife sister. However some may think an aunt
Since your mother and her sister have thesame aunts and uncles, your mother's sister's aunt is your grand aunt or, as some sat, your great aunt.
Sexual
You are First Cousins