Saoirse Ronan gets mean in "How I Live Now," and not at all in the same way she did for roles like hers in "Hanna." She plays an city-girl American inserted into the sweetly chaotic countryside in England, and comes with all the baggage of a structured, image-obsessed, angst-ridden teen.

"One note that [director Kevin Macdonald] gave me," Ronan said in our interview, "is 'Bitch it up a little bit, Saoirs', bitch it up.'"

Ronan said her (ironically named) character Daisy had a look that helped inspire how she acted -- leather jacket, bleached blonde hair, black nail polish and piercings -- but still "it was a little bit hard to keep that up," to remain so harsh.

When the pastures are plunged into a war with unnamed enemies, it was McDonald's turn to use visuals of war-driven terrors to change Daisy's narrative. She suddenly starts living life under military rule, separated from her country-bred beloved Eddie, with merely surviving and struggling back to a home she fell in love with topping her to-do list.

"We live in anxious times, we're all worried all the time," McDonald said of the timing on this film. "That's one of the whole marks of our age, we think a bomb could go off at any moment, somebody could put poison in the water. The thing is, you don't know who's going to do that. That's part of the paranoia of our times."

Ronan also took a moment to compare this film to one of her next projects, the Nick Hornby-penned, John Crowley-directed immigrant tale "Brooklyn."

Watch our whole interview, on that new film, the American and British-ness of "How I Live Now," and the non-confirmation on the "Fantastic Four" casting. 

"How I Live Now" is out today (Nov. 8).