Q: How did you approach your character, Maria, the big actress that you're playing? It's a role that you already know...
J: it was exhilarating to play this role, like a hide and seek game. I don't think I am as moody as Maria, but one of the common points that I have with her is that I love to throw myself into roles. And this role was a challenge. The love story that she has to interpret in the play and that she repeats with her assistant [Played by Kristen Stewart] is troubling, because it's two different ways of acting, we never know if the feelings between her and her assistant are real or not. It's a theme that I got to explore in "Copie Conforme" by Abbas Kiarostami: two strangers that meet each other for he first time and have to pretend to be married. (...) The films "Sils Maria" has a lot of different themes, but the one that appeals to me the most is the transformation of my character because of the confrontation with the younger actress played by CGM, who plays the role that she played twenty years before. Maria can't act like she used to, she can't hold on to the past, she has to reach a new level, she's confronted to her fear of change and she can only achieve that by accepting her difference.
Q: Kristen Stewart is mesmerizing and really throws everything back to you. Is it a beautiful encounter for you?
J: I saw her in "On The Road" by Walter Salles. She has a natural sensuality and an unparalleled sensitivity. At one point, Olivier hesitated, because he wanted to give her the role of the young actress and Kristen refused, she wanted to play the assistant. At first, she was a bit scared, but with time, she found her place. With Olivier, we shared a complicity by watching her blossom. Kristen has a huge potential, a stroke of genius, a capacity to read a text three times and know it by heart. We loved playing together, we had a lot of fun, because I was playing the star and she was the assistant. We're going to film another movie together in the film in a totally different register, a comedy by Steven Shainberg: The Big Shoe.
Scans and translation thanks to @SomeLostBliss