Heather Mills is refusing to let step daughter Stella Mccartney see her half sister BEATRICE, after reportedly hearing a taped phone conversation in which the fashion designer labels her a "liar". Mills, who split from former BEATLE Sir Paul McCartney in May (06) after four years of marriage, is threatening to apply for a court order banning Stella from contacting her two-year-old daughter. A close family friend tells British newspaper the Sunday Mirror, "Heather and Stella are at war. It is as simple as that. The pair have disliked each other for years but always put on a brave public face for Paul's sake. But now it has gone nuclear. "Heather is absolutely furious with Stella and does not want Bea to see her - ever again. This is no idle threat. Heather means every word and is fully prepared to go to court to stop Stella seeing Bea. "Paul is absolutely in bits about the whole thing. He adores Stella and has been relying on her since his marriage breakdown, while Bea is his baby girl - and she means the world to him as well. "The thought of him not being able to see two of his daughters at the same time is heartbreaking."