Hell no, that's incest.. Do the research it is DEAD wrong.
Your great uncle's daughter would be your aunt.
To your sister's daughter you are an aunt (or uncle) and she is your niece. To your niece's daughter ( your sister's granddaughter) you are a great-aunt (or great-uncle) and she is your grand-niece.
Since your uncle's sister is your aunt, her daughter would be your cousin, just as your uncle's daughter would be.
You are her great-aunt/uncle. She is your great-niece.
She is you niece and you are her aunt or uncle.
Your brother's daughter is your niece. You are her Aunt or Uncle.
Your uncle/aunt's son/daughter is an adult and you are still small, your uncle/aunt's daughter had a child, and that child will call you uncle. Uncles/aunts are your dad/mom's siblings.
You are the great aunt/uncle
their aunt or uncle
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.
Your sister's daughter is your niece, so you are her aunt or her uncle.
Your daughter and your aunt's children are first cousins to each other. Your daughter and your aunt's grandson are first cousins, once removed, to each other.