The Lady Killer by Rod Gray

Eve Drum works for top-secret spy organization L.U.S.T., her archenemy is the evil organization H.A.T.E., who don't actually show up much in the novel. Eve is a gorgeous blonde with knockout measurements who lives in a Manhattan penthouse. She poses as a worldly, well-to-do socialite, and is even made temporary detective in NYC. She is on the hunt for The Lady Killer, who is murdering a group of four doctors, one by one. They invented a new, stronger form of methadone are being killed off by a sadistic redheaded female assassin. Eve must figure out who is behind the plot and how to stop further killings.