yes it is
If she is your sisters daughter then she is your neice :)
She is your niece.
She is your niece.
Niece.
niece
She would be your niece.
Your brother or sister's daughter is called 'your niece.'
If he is your brother in law then his sister is your sister in law. So your sister in law's daughter would be your niece.
Your sister's daughter is your niece and you are her aunt (if you are a woman) or her uncle (if you are a man).
Your brothers ( or sisters ) daughter is your ( niece )
Your sister's daughter is your niece, her granddaughter is your "great niece"... or you could just call her by name.
Your niece