You vote for the person you think is horrible and then you have to live with the person you think is horrible. Shock Horror
Never even occured to the Others that they had just put the 'horrible' person into 'their' group. They all sat around thinking 'Hey this is awkward for Jayne her fling with a married man just walked through the door'.
Meanwhile Chelsea sees someone he knows and decides to play it as if he has never met her before in his life. Which from the way the first day greetings were acted they already seemed to have met before.