The Hollywood star is still struggling to come to terms with the 16-year-old's death, six months after he suffered a fatal seizure on a family vacation in the Bahamas.
But Preston is intent on throwing herself back into acting, and has signed to play mother to Cyrus' rebellious character alongside Greg Kinnear, who will play the Hannah Montana star's estranged father.
Preston has rarely been seen in public since the loss in January, while husband John Travolta pulled out of media promotion for his new movie The Taking of Pelham 123 as he couldn't face reporters' questions.
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