Is boarding school the right option for a distant child who has been abandoned by her mother?

by Anonymous
(New Zealand)

I am the eldest of three children. I live in New Zealand and my mum moved to the other side of the country with her partner. She left us to live with other relations. I'm 16 and live with my aunt, the second youngest whose 14, lives with our dad and the youngest, she's 12 and she lives with our grandmother. We are all not very close to our parents but however my sister (the youngest) is closest to me and is very distant to everyone else; where as my brother and I are still close to other members of the family.

As said in that video about child survival roles, I am the parentified child; my brother is the rebel child and my sister a mixture between the lost child and the mascot. She is always off in her own fantasy world and is never paying attention to her surroundings, but she also likes to be performer and make people laugh. She is not very independent and always relies on me to do things for her and to tell her what to do.

We are looking at sending her to boarding school to make her more independent and our grandmother is getting too old to look after her. However I do not want her to become even more distant from the family and view it as more abandonment.

Do you have any suggestions about what to do?