Seriously Sienna

Sienna Miller graces the cover of Vogue's July issue. - Craig McDean/VogueSienna Miller has grown up quite a bit since appearing on Vogue's September 2007 cover. The then 25-year-old actress espoused her many self-assured wiles but seemed on the cusp of maturity. "I want to grow up ... I don't want to repeat patterns," she admitted, before adding, "I'm young and I need to have fun!" Now 27, Sienna shudders when she thinks back to the actions of her youth, such as calling Pittsburgh "Shitsburgh" while filming in the city.

"I wanted to be conscious of my actions," she shares in the July 2009 issue of Vogue. "I think I was really naive ... thinking that if you are true to yourself, that's enough, that's the best way to be. But, actually, it's more important to become more conscious."

Although Sienna struggles to shake her reputation as being a party girl, Jude Law's ex, and an indie-flick-only chick, she is ready to go from It girl to hit girl. Not only is she taking on a Hollywood blockbuster -- "G.I. Joe: The Rise of Cobra" -- but she will also be making her Broadway debut in "After Miss Julie." Get a sneak preview of Sienna's interview with Jonathan Van Meter, who has this to say about the actress: "Her hotel room is like her life: complicated, messy, public, fun."

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On her nude scenes in the ill-received flick "Mysteries of Pittsburgh" (2006), alluding to the Jude Law "Nannygate" fiasco:
"I don't think I feel comfortable getting naked now. I can see where I made the decision to make that film three years ago, but then you grow up and evolve and your tastes change. I was in this period where I was making movies back-to-back because I didn't want to be at home. Anything not to be in London. I was running away."

Sienna may shed her indie-flick rep with her starring role as the Baroness in "G.I. Joe: The Rise of Cobra" this …  

On Jude Law cheating on her with his nanny while they were engaged:
"That was a very pivotal time in my life, and I'm happy saying that. It's a private moment when you get your heart broken for the first time, and that was the absolute antithesis of private." She starts to laugh. "It couldn't have been more public! I had people on the street being like, ''Ang in there, loov!' and all you want to do is crawl into a cave and weep for a week."

On her bad-girl reputation and public perception:
"I've made some bad choices and done some stupid things."

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On dating:
"I've actually never been taken on a date in my whole life. I have never had a one-night stand. I'm a real relationship person -- contrary to public perception. I'm either in one or I'm not. I get kind of emotionally involved very quickly, and I'm not going to spend time with someone unless I love them. But it's not hard for me to fall in love."

On starring in a blockbuster like "G.I. Joe," which had a crew of 1,000 and was full of near constant explosions:
"Initially I was terrified," she admits. "It was so out of my comfort zone. Everything gadget-wise that I had to use actually worked. I had these little guns, and if I fired them, lights came up and they made a sound. It was Disneyland for grown-ups."

Read more of Sienna's interview at Vogue.com, or pick up the July issue of Vogue, which hits newsstands nationwide on June 23.