'The Vampire Diaries' explores the theme of there being good and evil inside everyone, and how everyone has a different level of acceptance for that fact. The Vampire Diaries - Season 3, Episode 19 - "Heart of Darkness"
Liz has stated previously that she still sees her daughter in Caroline. So one would think that Liz would want to leave Caroline as the last vampire to take down after Stefan and Damon
The Vampire Diaries moves to Fridays on January 29, and The CW has released two promotional images and an official description for the first episode in the new slot.