It must be noted that the narrator's observation was imperfect. He suspected his eventual love interest of being loyal to the party because she appeared as a "bigoted adherent" when in reality that was a cover for her secret rebellion. So the line quoted was disproven by the remainder of the book. I see it as an acknowledgement that women have historically had so little power that they had to play along with those in power to survive. Women, already accustomed to lay with the same enemy they were fighting against (i.e. men), adapted that duality in response to the political climate. They were adept at feigning solidarity to survive.

I also view it as a recognition that women often have higher levels of religiosity and have historically been the enforcers of morality. Enforcing the social codes has been a way women could influence men when they had little political or legal power. I read it as Orwell saying that the political regime was able to co-opt women's tendency to uphold the social order and use it to further perpetuate their own cause.