A few nights ago I re-watched Casino Royale (CR) ... having recently seen Quantum of Solace (QoS).
In CR, M implies Vesper Lynd loved Bond because she agreed to deliver the money in exchange for Bond's life. (Just thinking about the 'chair with no seat scene' still make me shudder). In QoS it seems as though Vesper was also being played by her old boyfriend (who gave the necklace).
So here is my question: In CR, what control did her old boyfriend have over her? Was he working for Quantum? Why did she drown herself and not let Bond save her?