Board Thread:Show-Related Questions and Answers/@comment-26116863-20151117024202/@comment-26967699-20151117143307

She might think that she'll be able to kill her before she does anything. And if Zelena would be a Dark One, then killing her with Excalibur will kill her. Even Cora said that If Gold dies because of Dreamshade, he will expel the powers of the Dark One which means it will be destroyed.