The Oscar winner, 45, plays the late US movie star in Olivier Dahan's Grace Of Monaco.
According to leaked scripts, the Australian actress portray Grace, who married Prince Rainier III (played by Tim Roth), as the lonely and desperate victim of an abusive husband.
Grace's son, Prince Albert, and his sisters Caroline and Stephanie, have said the storyline is riddled with "major historical inaccuracies and a series of purely fictional scenes".
Kidman defended the film saying: "I wanted to be respectful of her, her story and her essence so hopefully that will all come through.
"It's exciting but at first it was daunting. At the same time I had studied her and felt a kind of tenderness towards her."