Shes you Aunt in law!
She can't stop you from sleeping with your husband.
you call her your daughter's husband's sister
You don't call your brother's sister your aunt. Your brother's sister is your sister, or you. Your aunt is the sister of your mother or father.
You would call your mother's sister an aunt.
You would call your sister's daughter your niece.
Your child would call your sister her aunt.Your sister would call your child her niece or nephew depending on gender.Your sister's children would call your child their cousin.
sister = sahodari older sister = chechi younger sister = anujathi
sister in law
The relationship of the sibling of your sister-in-law or brother-in-law to you does not have a name in English. You could call them your brother- or sister-in-law if you want, or you can call them the brother or sister of your brother- or sister-in-law.
sister in law
You would call your sister's husband your brother-in-law.
Your sister's son will call you his uncle, if you are a man, or his aunt, if you are a woman.