What relation are you to your aunt by marriage niece?

Answer 1

There is no relation between you, and your biological Uncle's wife's sibling's daughter.

Your Uncle's wife is technically an "Aunt in law", though as routine courtesy is simply called "Aunt". Her brother/sister, if your family and her family are that close, could be regarded as an "Uncle/Aunt in law", as a stretch. Thus the daughter of him/her could be thought of as a "cousin in law" to you.

But this is all a matter of courtesy, there is no biological or legal relation.

Answer 2

Your aunt's sister is your mom or your other aunt, or no relation at all if your aunt is your aunt because she married a brother of one of your parents.

Answer 3

Your uncle's wife is your aunt. Her sister is not related to you, neither is her daughter, even though your uncle is also her uncle.

Answer 4

Your uncle's sister is your aunt, or your mother.