I think it very likely that Evie had every intention of avoiding the immediate threat (by agreeing to the deal), working out whether additional evidence or copies existed anywhere, and finally betraying and eliminating Rachel later after she was reasonably sure that she had all the evidence in hand. But that doesn't matter now. :-)
Shout by FernandoBlockedParentSpoilers2016-06-20T00:16:37Z
Evie shouldn't have made the deal. She had no prove that that was the only copy of the video. It's a little hard yo believe, but anyway.