The vote was actually really close by a percent between Megan and Stephanie and/or Jeremy (can't remember how many it was actually close between). I think Stephanie survived because of how hated Gemma was and that some saw Stephanie as in the right against her. She was also as big a character as the likes of Tiffany, Gemma and John so that helped. Jeremy I think just got really lucky as some annoying sympathy vote even though he was just as guilty as Stephanie and even took advantage of her
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And Gemma got hated because the first two weeks she was a lot more normal and level headed compared to how she was later, as well as the public having such a grudge against John (that I still can't understand). But then they hated how lazy she was getting, her arguments were really over the top and negative, she was doing a lot more attention seeking, etc.