Character Analysis
I-330 is a regular "Mata Hari," a dangerous woman serving as a spy and a corruptor. It stems from the name of a German spy in the First World War, and yeah, it's a little patriarchal, but what are you gonna do? I-330 is the Future Girl equivalent of the femme fatale, twisting men around her fingers and getting them to do her bidding. D-503 hates her initially, claiming "the woman had a disagreeable effect upon me, like an irrational· component of an equation which you cannot eliminate" (2.35). But her charms are irresistible, and he ends up falling for her. Hard.
We're never entirely sure if I-330 truly loves D-503, or if she's merely playing him for her own ends. Having said that, at least those ends are noble ones. As a member of MEPHI, the underground organization dedicated to overthrowing the State, she has big plans for free humanity from its self-imposed enslavement, and it shows in everything she does. She commits little acts of rebellion. Like the time that D-503 "noticed a bottle filled with something poisonously green, and two small glasses with thin stems. In the corner of her mouth she had a very thin paper tube; she was ejecting smoke formed by the burning of that ancient smoking substance whose name I do not now remember" (10.24).
That passage actually shows a lot about her character. Not only is she engaging in the forbidden practices of smoking and drinking, but because she has two glasses instead of one, she wants to spread the rebellion. Judging by D-503's response to her, she does a very good job of it.
That ties into her status as an iconoclast in a world of conformists. She may not live to see her rebellion come to fruition, but she's going to do everything in her power to make it happen.
As for the question of her loving D-503, it really doesn't matter. For even if she truly loves him, that too is an act of rebellion against the State: something she probably picked up on at a very earlier age. She loves him or she's just using him; whatever it is, it's supposed to help spread the madness of freedom just a little farther.