Elle Fanning Will 'Try Not to Annoy' Sister Dakota While Filming First Movie Together (Exclusive)

"We must treat each other like fellow actors," Elle told TooFab exclusively of her upcoming project with older sister Dakota, which will mark as the siblings' first time officially working together.

Elle Fanning admits she will have to change some things about her process before working with her sister Dakota.

While walking the carpet at the Los Angeles premiere for her upcoming film, Sentimental Value, the 27-year-old opened up to TooFab about her upcoming project with her older sibling.

The pair are set to star together in a film adaptation of The Nightingale by Kristin Hannah. The movie will follow the sisters as they play siblings coming of age in France during World War II. It will be the sisters' first time working together officially; they have technically been in the same film before, when Elle played the younger version of Dakota's character Lucy in I Am Sam.

Dakota told ExtraTV that she will need to dial down the "bossy" older sister vibes on set when they begin production, something Elle reacted to when TooFab spoke with her on the carpet on November 5.

"She better," Elle told TooFab. "She must, we must treat each other like fellow actors."

While Elle believed there were things she will "definitely" have to change as well, she knows the pair will benefit on screen from their sibling relationship.

"The thing is, we are playing sisters," she continued. "So, we can use it in our characters. But you know on set, I don't know, I'll try not to annoy her."

The Fanning sisters broke into Hollywood when they were both children, Dakota at 5 years old starring in commercials and a guest role in ER, before landing her breakthrough performance in I Am Sam. Elle, on the other hand, was just 2 years old with her first onscreen performance being I Am Sam, before landing her first major role in Daddy Day Care.

Now, with over two decades in the business with Elle in her late twenties and Dakota, 31, Fanning fans will finally get to see the sisters share the screen. It will be a change for both of them to see how the other works on set, letting one another into their acting process because they haven't so much as read lines together over the years.

"Never, we have to get over that," Elle added.

Sentimental Value -- which also stars Stellan Skarsgård and Renate Reinsve -- follows the story of a father, Gustav (Skarsgård), who attempts to reconcile with his estranged daughters after their mother passes by writing a film in the hopes of casting his one of them in the project (Reinsve). She rejects the proposition, prompting him to cast Hollywood star Rachel Kemp (Fanning).

TooFab asked Fanning if there has been a role in her career that has helped heal areas of her personal life.

"I mean certainly," Elle begun. "I think playing many characters over the years have healed things in me that I didn't expect and that's why I love acting."

She continued: "You get to work through emotions and traumas perhaps that you can't necessarily work through in real life. But through the character you can kind of bring those emotions out and understand what you've been through yourself and what happened."

Elle added that during her time on set of Sentimental Value she noticed a change in her ability as an actor, as she worked through personal emotions.

"I think that happened to me a bit on this set," she told TooFab. "I definitely felt myself learning and growing and stretching more as an actor especially working with [director Joachim (Trier)."

Sentimental Value releases in theaters November 7.