She is your aunt. This is true in most traditions. English does not distinguish between an aunt by marriage (father's brother's wife) or an aunt by blood relation (father's sister).
Your father's brother's son is your first cousin and your daughter's second cousin.
your 5th cousin
granddaughter
aunt
cousin!
Cousins
Are you asking what you call your brothers daughter? Well if you are your brothers daughter is called your niece.
Niece
A niece
A niece
That would be your Cousin.
natini