T-this didn't happen on Momoclo-chan...!! (Although I would enjoy seeing a segment/competition where last "adult" standing wins, without the death part.)
^ I have a feeling the correct answer for Shiori's was "long hair" and her pride and dedication to keeping her hair short since 2011 urged her to choose the wrong one, and she knew it was wrong since she told Kanako goodbye before "dying". As for Momoka, I bet she chose on a whim and hoped for the best, lol.