Wendy Mericle answered the question for this week’s Ask Ausiello:
I am excited to have Katie Cassidy back on Arrow as Black Siren. I hope she stays a villain, because it’s cool to have a regular female villain. What can we expect for her?
Ausiello: You can expect much of the aforementioned villainy, sprinkled with the occasional wish for a turn-around, at least by those who knew her Earth-One doppelgänger. “I don’t know if there’s any question about whether or not the [idea] of redemption will come up; it has to,” co-showrunner Wendy Mericle told TVLine. “Her father is there. Oliver is there. Everyone is going to be asking whether or not it’s possible to find a little piece of Laurel, the Laurel Lance they knew and loved, in there somewhere.” That said, “I think she’s interesting as a [villain],” Mericle asserted. “Black Siren is a badass.”
– UPDATE –
How will someone like Black Siren feel about Dinah suiting up as Black Canary?
Mericle: That’s a great question. I’ll just say this: She’s probably not going to like it very much. [Laughs] I mean, I don’t know how much research she’s done about her Earth-1 Laurel, but I would have to say that I think there’s going to be some sparks flying there.