Complex sentence: Piper and Billie both lived, Phoebe's body was found and it was concluded that Christy died because Leo was returned yet Piper says in the next episode that both of her sisters have died.
Split into simpler sentences: Piper and Billie both lived, Phoebe's body was found and it was concluded that Christy died because Leo was returned. Still, Piper says in the next episode that both of her sisters have died.