Cindy was always an "other". She didn't become an "other", she was already among them, and was a plant on 815; a plant whose primary purpose was to give Jack those two Vodka bottles. I submit the idea that we will see a scene involving the prepping of Cindy, as she is briefed on who the essential passengers are, and what her roll will be. The scene will include Fristian (Fake Christian for those who don't know) handing Cindy the two bottles, indicating that it's "Special Vodka", not just ordinary Oceanic inventory.
