We have kinda known of actress Marion Cotillard's "attachment" to Christopher Nolan's, Batman: The Dark Knight Rises for quite a while now, we even had an idea of her role[s]. When it was finally confirmed [to little surprise] that the actress was involved in the movie, her character was listed as "Miranda Tate", a member of the Wayne Enterprises board "eager to help a still-grieving Bruce Wayne resume his father's philanthropic endeavors for Gotham."
There has been signs that Cotillard was in fact going to play Talia Al Ghul. for some time and her "Miranda Tate" was just a cover. 24 Frames put the question to her, "My role is a secret, as is the whole project."
Not very revealing but the actress did open up a little on rejoining Nolan on this project, and what drew her to Batman:
"Cotillard did offer some thoughts on why she joined the film -- namely, a chance to reunite with Nolan. And she said she has a specific regard for Batman among pretty much all the superheroes out there. Just what is it about Batman that makes him so appealing to the actress? It's that brooding thing. "I think it's that he's human," Cotillard said. "He can't really fly, and he doesn't have superpowers. And he has that darkness inside."