User blog comment:The Unknown Sister/Laurel Cliffhanger/@comment-28458080-20161208202437

1 She is Black Siren who escaped from Prometheus who wanted to kidnap her.He thought she was E1 Laurel and wants to traumatize Oliver

2 She is a hallucination because of a drug Susan Willians gave him or just because Oliver feels he isn't a hero

3 She is the real E1 Laurel who either faked her death or got resurrected by Flashpoint/Alchemy but still remembered she died in the original timeline.