There is no relationship at all.
She is your third cousin.
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.
The daughters of your sister are your nieces.
She is your niece, you are her aunt or uncle.
Technically there is no relationship. When introducing her, you would refer to her as My daughter's mother-in-law.
The sister of your mother-in-law and her children are not related to you.She is your children's aunt and her children are first cousins to your children.
I call her Jane. There is no special name for a person in that relationship.
Tuthmosis ii.
You would call your sister's daughter your niece.
notin just another person. unless she marry s him Even if she marries her boyfriend then there is still no relationship name.
You would be his Great Uncle or Great Aunt He in turn would be your Great Nephew.
yes she can