Kelly Brook insists on starring alongside fiancé Billy Zane, because she can't bear to see him with other women. The 26-year-old model turned actress, who starred opposite Billy in 'Three' and new film 'Fishtales', has admitted she is too jealous to let her fiancé film steamy scenes with other gorgeous actresses. Kelly told Britain's You magazine: "If he had Mischa Barton or some other lovely young girl as his leading lady, he wouldn't have got any dinner."People think it's cheesy but we love each other, so we made a pact: you make the dream happen."The curvaceous British actress admitted her breasts have helped her career. Kelly believes her sexy image, Hollywood success and engagement to Billy Zane is all down to her chest. She said: "I am what I am. When you have big boobs and a bum, you are going to be cast as the sexy girl all the time. But I'm not averse to that. I've always been grateful that I've been able to make the most of it and keep working."