In Part II Chapter II Winston takes the high risk of meeting Julia for the first time. He cannot be completely sure that she is not a member of the Thought Police and that he is being lured into a deadly trap, but such is his desire for female companionship and finding like minded anti-Party connections.
Winston discovers that Julia is a high spirited, anti-establishment citizen who is highly skilled in the artifice of maintaining the front of being a loyal Party member. She does this through voluntary involvement in some of the many organized Party activities,
"Actually I am that sort of girl, to look at. I'm good at games. I was a troop leader in the Spies. I do voluntary work three evenings a week for the Junior Anti-Sex League. Hours and hours I've spent pasting their bloody rot all over London. I always carry one end of a banner in the processions." (p. 128)
Julia has no genuine belief in the Party and commits small acts of rebellion (casual sex, accessing goods on the black market), but she is also clever enough to know that she must maintain her veil of loyalty at all times if she is to survive in this society. She explains in part how she does this when she says that during her volunteer activities,
"I always look cheerful and I never shirk anything. Always yell with the crowd, that's what I say. It's the only way to be safe." (p.128)
She has calculated that the only way to survive, the only way to be safe, is not to just go about your business (as Winston does) but to pro-actively pretend to support the Party and be noted as a true loyalist.