User blog comment:Chrissh/If I was on the Worlds Apart Jury/@comment-161.28.248.174-20150424181850/@comment-26288837-20150425015919

Sierra flipped because she realized Mike is a sinking ship. Sierra is just trying to ride coattails to the jury vote. Mike is the biggest threat in challenges, as well as a likely winner at the jury vote, so he has to go. Sierra is smart enough to realize it's time to ride someone else's coattails.