Stella McCartney reportedly threatened to kill her stepmother Heather Mills during a heated row with her father Sir Paul McCartney. The fashion designer, who is currently pregnant with her second child, allegedly made the threat after learning that Heather had claimed that Paul had been physically abusive towards Stella's late mother Linda during their marriage. According to Britain's News of the World newspaper, a hysterical Stella had to be restrained by father Paul as she screamed: "I'm going to kill that bitch. I can't believe what she's doing to you."Stella, 34, then reportedly launched into a tirade directed at Heather,fuming at her ex-Beatle father: "I told you she was a bitch. Why did you marry her? She's been a manipulative cow from day one. She won't be happy until she destroys all of us - and our memories of our mother. "The bust-up between Stella and Paul occurred at the McCartney family's Peamarsh home, in the UK, during a meeting which had been arranged to discuss 64-year-old Paul's impending divorce from former model Heather, 38. Earlier this month, Heather also accused Paul of being "physically violent"towards her. Among the most serious allegations made in court papers lodged by Heather's lawyer included accusations that Paul pushed her into a bath while she was pregnant, pushed her over a coffee table and poured wine over her head before allegedly stabbing her in the arm with a broken glass.