One way in which it is possible to argue this statement is to look at the way that the Party has perverted and twisted relations between the genders to create female characters who are very different from those normally encountered in literature. This can be approached best through the character of Katharine, Winston's wife, whom we meet in his memories of her in Part I Chapter 6. Winston quickly concludes that actually she is the dullest and least intelligent person he has ever met, and note his assessment of her:
She had not a thought in her head that was not a slogan, and there was no imbecility, absolutely none, that she was not capable of swalowingif the Party handed it out to her. "The human sound-track," he nicknamed her in his own mind. Yet he could have endured living with her if it had not been for just one thing--sex.
Because the Party says it is the duty of married couples to try and procreate, Katharine calls sex "our duty to the Party" and "making a baby," but she treats it like an unpleasant job. She is an interesting example of a female character that has let the Party erode all of her femininity. Winston's memory of Katharine in the novel is used to show how the Party tries to control all forms of relationships, and even the sexual relations within those relationships. Katharine is an example of a "twisted" form of femininity in that she seems stripped of the normal qualities associated with women in literature: she is not loving, sensitive or passionate and lives to serve the Party alone. The Party's impact on gender is thus demonstrated.
However, having argued this, it is important to consider the ways in which Julia is not presented in this way, and also the memories that Winston has of his mother and sister. Katharine seems to prove that female characters are presented in a twisted form, but the other female characters do not suggest this.