I was reading your post and I think the niece you are talking about is my mum. My mother was born in Sa'a sai she went to New Zealand in 1962, she was born in 1943...my mum is still alive, she is 70 years old now. Her name is Tusipauna Fuapepe Sa ( family names also include: Vagana, Sa, Simei & Vaafusuaga) my grand mothers name was Talaitupu O Samoa Vaafusuaga and she had seven children Tusipauna, Talatau, Sofai, Ieremia, L'ia, Po'o, Fa'amuli (five boys & two girls)
My great grandmothers name was Fa'afiatauli Vagana Simei...my mother was the oldest child of Talaitupu, my mother is probably the oldest living relative since my grandmother passed away. They used to call my mum Tusi for short.