Cameron Diaz is in final negotiations to topline Warner Bros.’ legal comedy “Bobbie Sue,” with Donald De Line producing.Story centers on a hard-charging female ambulance chaser whose mindset makes her the ideal candidate to be the face of a prestigious law firm when a powerful client is sued in a sexual discrimination case. Warner bought the spec script by Russell Leigh Sharman, Owen Egerton and Chris Mass in the fall. Dana Fox is polishing the screenplay. De Line senior VP Andrew Haas is exec producing “Bobbie Sue.” Warner-based De Line produced recent releases “I Love You, Man” and “Observe and Report” and is developing “Yogi Bear” with Karen Rosenfelt. Diaz will be seen next in New Line drama “My Sister’s Keeper” with Alec Baldwin and Abigail Breslin.