Not so says CBBC Newsround, who claims that Helen McCrory has now been offered the part.
Helen McCrory for Harry Potter and the Half-Blood Prince
Helen McCrory was originally set to play Bellatrix Lestrange in Order of the Phoenix but was forced to exit due to pregnancy. All was fine, however, as Helena Bonham Carter became the upgrade replacement.
So now McCrory is back again and she is hoping to don the albino-white hair as Narcissa; all of the Malfoy's are er, fair. She and Carter will now be sisters.