So at the very beginning, Amber Heard is brought in to assassinate The Wolf. We have to assume she is a highly skilled agent on an important assignment.
But then instead of killing The Wolf, she follows Costner to Paris and blackmails him into killing the Wolf for her? Huh? Suddenly she is not a skilled operative, but has instead turned into a client who hires other to do her dirty work?
Yeah, that made no sense whatsoever.
I kept thinking that I must have missed something, or maybe dreamed that whole opening scene, where she is assigned the Killing-The-Wolf job, because her blackmailing Costner to do her job was just..... like... HUH??!!
Vivi didn't know what The Wolf looked like. That's why she didn't kill him back at the hotel. So, she followed Ethan (the only survivor of the hotel bombing) back to Paris and hires him to find and identify The Wolf. She believed that if Ethan were to cross paths with The Wolf, he'll recognize him.
As for the part of getting Ethan to kill The Wolf for her; that was just Vivi's way of assuming control. She's a control freak. That's why she seemed so interested/infatuated with Ethan. He didn't always give in to her. And he never made a move on Vivi despite her efforts.
"You're an idiot." - Irisa Nolan, Defiance (2013)