a book i forgot about a crazy twin

[booklover200]

This book is about two twin sisters when one dies other twin has take over the other live.the twin that takes over the other life was sent away because her parents thought it was for her best because her twin sister was crazy and scare people with rats.

[racheling · Accepted solution]

Hmm, could it be this one? User reviews mention the living twin had been sent away.

Twins 

Mary Lee and Madrigal are identical twins, two halves of one whole or so it seems. But when their parents send Mary Lee to boarding school she feels lost and alone. Mary Lee wishes she could live Madrigal's life. But then her wish comes true and she finds out just how different Madrigal was.