The actress tells Nylon she revels in breaking society's rules. "Life's really short," she says.
"A lot of what we do is a reaction to what people think you're supposed to do - 'Have a kid at 30. Move in, but live together for at least this amount of time.'
"All of those rules I want to rebel against. Because I'm a spiteful little sh*t, basically."
The 32-year-old told the magazine that she moved in with actor fiancé Tom Sturridge, the father of her baby daughter Marlowe, "after two weeks" of dating.
The Layer Cake star also says she felt "let down" after giving evidence in the phone hacking trial in the UK.
"I feel very let down by that system, but there is a more important thing going on: this conversation about hacking people's phones and privacy.
"I'm really proud of the things I've done standing up for myself in that way.
"But it doesn't make it easy that suddenly Jude [Law] and I are back on the cover of every newspaper in London."
Indulge in a bit of Sienna Miller style stalking right here:
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