Sienna Miller is currently promoting Kevin Costner’s Horizon, a Western saga where Sienna plays a rough-and-tumble pioneer woman. Costner really wanted Sienna for the role, she was his first choice and that worked – she was flattered, and she’s been singing Costner’s praises for months now. Sienna also recently welcomed her second child, another daughter, with her boyfriend Oli Green. Green is 14 years younger than Sienna. She still sounds bummed about that, but she also seems at peace with her life right now. She’s no longer the hunted paparazzi target and she’s no longer the callow party girl. She’s matured into an interesting actress and a mother of two. Some highlights from her Harper’s Bazaar UK interview:

Why she signed on to ‘Horizon’: “Kevin sent me the four scripts, and they were astounding, almost Tolstoyan in length and detail. They hooked me. Then he asked to Zoom, and I was thinking, ‘Be still my Nineties heart!’ because I had been obsessed with Kevin Costner growing up. He was my first love. So, we talked, and he was very complimentary. He told me the story of the film and got to know me a bit. At the end he said, ‘Sienna, I have one question for you: will you go West with me?’ I died. I said, ‘I would go to Mars and back with you, Kevin.'”

Her fortitude: “If there’s one thing I’ve gained from the life I’ve led it’s a sense of resilience, fortitude – which sounds like I’m complimenting myself, but that’s not how I mean it. It’s like being forged in fire. I would have loved to have not been forced into that resilience, but I have, and that’s a part of myself that I brought to [my Horizon character] Frances.”

Flying into NYC for the Met Gala: “We flew to New York on Sunday with our nanny and, on landing, she got deported. So it was a random scramble of trying to find a babysitter, and stressful because I’m breastfeeding. It was a bit of a trip.”

Falling for Jude Law & becoming an It Girl: “That happened very quickly. The other side of it. I was so happy in my life, but it was weird, surreal. At first it was like a game. And then, very quickly, it became insidious and difficult.”

As she lost her privacy, she partied: “I was probably drinking too much, medicating in all sorts of ways, because it was jarring and scary. I was desperate to have roles that were intense, to prove that I was more than a fashion plate or a girlfriend. I just wanted be taken seriously. But, really, there wasn’t much conscious decision-making. I had a decade-long case of the f–k-its. Which is kind of cool, I suppose, and intriguing, but maybe not conducive to getting your career going – ie, what I was meant to be doing.”

Welcoming her second daughter with Oli Green: “I’m in heaven. It’s been a cathartic, healing experience, which sounds woo-woo, but it’s grounded in a way that reflects the life that I want to be living,” she says. Miller also did not intend to fall in love with Green, whom she met at a Halloween party and who, at 27, is 14 years her junior. “I didn’t expect to take it seriously and then quite quickly, I fell in love. I wasn’t like, ‘I’m gonna get a younger boyfriend.’ It was more, ‘F–k! Why are you young? That’s so annoying.'” She was surprised, she says, by how soothing it is to be with a younger partner. “There is a difference in the way that generation of men respect women. It’s specific to him, he is very wise and well-adjusted, but I do believe it’s also that generation. They have grown up with a slightly more level playing field. I see it in his female friends as well as in the men.”

The dark side of the ‘90s: “I could talk myself into all sorts of shapes to make the men in the room feel comfortable. And God forbid that you offend a man’s ego by rejecting them. It was a slightly belittling time. It’s interesting, being older now, and having been raised in that moment, learning from people who are younger about how clear they are in their boundaries, having that self-assuredness and self-advocacy, having ‘no’ in the repertoire in a way that we just weren’t encouraged to have.”

[From Harper’s Bazaar UK]

I’ve said this before, but I think Sienna’s thing with Oli Green works so well because she never expected it to work at all. She had no expectations and she had arranged her life to the point where she was fine with being a single mom. She knows that she’ll be fine if this relationship ends, which changes her attitude, I think. She’s the mature one, she’s the one “leading” the relationship. I really feel her on the ‘90s stuff… while I look back at the ‘90s with rose-colored glasses, I’m often confronted by just how f–ked up and sexist everything was back then.

Cover courtesy of Harper’s Bazaar UK and photos courtesy of Avalon Red..