In 2015, Kristen Stewart became the first American actress to win a César Award, the French equivalent of an Oscar, for a role that was almost lost in translation: Valentine, the personal assistant to an aging movie star, in Olivier Assayas’s “Clouds of Sils Maria.”
“In this sort of very French way of doing things, they personally sent me the script,” Ms. Stewart recalled. “And it was beautiful. I loved it.” She waited for the filmmaker’s people to follow up, American-style, and they, assuming her silence meant she wasn’t interested, offered the part to someone else.
But “the stars just realigned in this very, very lucky way,” she said: The other actress had to drop out.
Now, in the ghostly “Personal Shopper,” in theaters Friday, March 10, Ms. Stewart is playing a role that Mr. Assayas wrote specifically for her. As the sullen, motorcycle-riding Maureen Cartwright, she selects haute couture for her celebrity client, who gives her blank checks but demands that she not try on the clothes.
But that’s just Maureen’s day job. A twin whose brother has recently died, she is also a medium in search of a sign — anything will do — that he is still by her side. At Cannes in May, “Personal Shopper” was booed at the press screening but went on to be nominated for the Palme d’Or, with Mr. Assayas sharing a best director win.
In a phone interview from Los Angeles, Ms. Stewart, almost 27 and warmly loquacious, discussed her intimidating facade and calling out President Trump on “Saturday Night Live.” These are edited excerpts from the conversation.
What is it about you that Mr. Assayas wanted for Maureen?
Initially I thought it was because we have an ability to communicate sort of wordlessly. But he said that he needed this person to be someone who was quite remote and somewhat androgynous but also had this vulnerability that was overtly sexualized. There’s a real duality to this girl. She was a twin. She’s half of a person. She’s trying to supplement that loss and figure out who she is within that, and also within this very strange, superficial environment, which is this fashion world that she’s drawn to but also repelled by.
Did the film’s mixed reception at Cannes bother you?
It’s quite a divisive movie. It’s not easy to describe. It’s not really easy to even describe your own experience with it sometimes — and that doesn’t bother me. It’s not that I don’t care. It’s just that I don’t mind being a part of something that is polarizing.
Why do you think people consider you intimidating?
Oh, man, I don’t know. I’ve witnessed other people be not received well or rub people the wrong way, and I feel like most of the time that’s coming from a place where that person is shy, and they’re actually trying really hard. I think when I was younger I was, straight up, just guarded — and maybe that came across like I didn’t care. But really, it was quite the opposite.
Mr. Assayas is one of many who have called you the best actress of your generation. Do those accolades matter to you?
It’s not something that would ever push me or pull me in any direction. I really love what I do. I would still keep making the work even if critics didn’t like it.
In 2012, Donald J. Trump tweeted about your relationship with Robert Pattinson. You took him to task in your recent “S.N.L.” monologue, which you ended by saying “I’m, like, so gay, dude” — what some have called your first public statement about your sexuality.
I’ve been really open about that for a long time. But I hated the idea that the details of my life were being turned into some commodity, so I was on full lockdown, total protective mode. As of late, it became really clear to me that as soon as you start hiding the fact that you’re dating a girl, it seems a lot different from hiding the fact that you’re dating a guy. Because in the situation when I had a boyfriend, I was just protecting myself. And in the situation where I had a girlfriend, it seemed like there was this implication of shame or something that I was so not O.K. with. And so I kind of opened that up a little bit — much to my chagrin to be honest, because I still completely disagree with the way that those details are thrust in the media and sold like popcorn. But yeah, I just thought it was pretty important. By the way, those terms — gay, queer, straight — they’re so black and white, I still don’t even really agree with them. It was just a simplistic way of saying, “I know you disagree with something that you don’t understand.”
Did he respond?
No, he didn’t. Which is kind of cool. [Laughs]