Is Ali really dead in Pretty Little Liars?

Ali is not dead, but her twin sister Courtney is. Courtney tricked her into switching spots with her. So Ali has been at the mental home while Courtney has been playing her and ruining her life. When Ali comes home she takes revenge by killing her own sister. After she learns all of the girls secrets from Courtney's diary, Ali haunts them with their own secrets in hopes they wont find out hers.
No