The Factory Girl actress took time out from shooting a movie in the US on Friday to testify in the phone-hacking trial 4,600 miles away in London.
She gave evidence via videolink from a base in New Orleans, Louisiana where she is currently filming scenes for new drama Mississippi Grind.
The court heard earlier this week that the now-defunct tabloid News of the World had exposed an alleged affair between Miller and Craig after illegally intercepting a voicemail message from the actress to the 007 star in which she said: "I love you".
Miller, who has already accepted a £100,000 compensation payout from tabloid bosses over the hacking scandal, told the court on Friday that she was close friends with Craig and it was "likely" she had left him the message.
She insisted she ends many calls to pals by saying "I love you", but when pushed during cross-examination over the nature of their relationship, she admitted they had been "briefly involved" adding: "It was a very brief encounter - he was my best friend."
Miller also expressed her frustration that the story of her relationship with Craig has been "allowed out of the courtroom" and turned into a "titillating bit of info".
Several former high-ranking members of the News of the World's staff - including ex-editors Andy Coulson and Rebekah Brooks - are on trial in London over the phone-hacking scandal. They deny all the charges.