Shizuka Namino

A Mazone spy masquerading as the Secretary to the Prime Minister of earth, Shizuka is a consummate manipulator who stages an assassination attempt on her boss, then frames Commander Kiruta for the crime, only to then break him out of jail and trick him into asking Harlock to give her sanctuary for her apparent treason. Shizuka's ultimate objective is to ascertain the mystery of the Arcadia's unidentified forty-second crewman, and then disable the ship from within. When her identity is discovered by Harlock, Lafresia abandons her, only for Harlock to grant her freedom in spite of her actions.

He rescues her after her own forces attempt to terminate her rather than let her return in defeat, but torn between guilt of failing the nation of her allegiance and feelings of admiration for her honorable enemy, Shizuka ultimately orchestrates her own death at Harlock's hands. Harlock never tells Kiruta (who was quite smitten with Shizuka) that she was a spy, and claims she died a hero during combat with the Mazone fleet. Shizuka makes an encore appearance of sorts in Endless Odyssey, re-conceived as a holographic assistant to Dr. Daiba. She has dark hair (a la the manga version of her original character) but the same dress and pendant.

Naturally, there's no way to reconcile these two versions as being the same person, so don't hurt yourself trying. (Source: cornponeflicks.org/harlock/mazone.html )