"We still love each other," she explains. "I think in a break-up, somebody has to be a little bit cruel in order for it to be traditional, but it's not been acrimonious in a way where you would choose to not be around that person."
"We don't live together, as has been reported recently, but we do half the time," she adds. "Everybody will stay over or we'll all go on holiday and that's because we genuinely want to be around each other. It's great for our daughter that she has two parents who love each other and are friends. He's definitely my best friend in the entire world."
Miller has recently moved with her and Sturridge's 4-year-old daughter, Marlowe, from London to New York City, confessing that the relocation has helped her "kick myself up the a**."
"I just like the idea that you come to New York and you do something," she says. "I just felt like it was so easy and all my friends are there, and we'd probably drink too much wine and go to the country for the weekend."
"It was all gorgeous and great, but I'm really trying to kick myself up the a** in some way, and New York is very good at doing that," she admits.
And though Miller has definitely come a long way since her career first started nearly two decades ago, she still feels the need to prove herself.
"I was a fashionable girlfriend before I was an actor," she shares of her headline-making relationship with Jude Law in the early 2000s. "And then, I think, without enough sense of self to really hold onto whoever I might actually be, I just sort of drifted."
But the British actress is definitely back on top now, and more determined than ever.
When offered a role in her latest film, The Lost City of Z, Miller made one thing clear to director James Gray: "I'd like to do your film, but first, I'm not going to play the wife."