In Part II Chapter 2 Winston has taken the high risk step of meeting with Julia in a secret place. Of course it represents an appalling risk for him, but he is understandably driven by both the need for companionship and the desire to find like minded citizens who are not blind followers of the Party.
Julia turns out to be a high spirited girl who delights in her ability to slip under Big Brother's watchful eye. Rather than be horrified when Winston confesses he wanted to rape and kill her because he first suspected she was a member of the Thought Police, she is thrilled at the success of her duplicity.
As a member of the Junior Anti-Sex League she wears a scarlet sash and she tells Winston about some of her involvement with the group,
"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." (p.128)
The existence of an 'Anti-Sex League' gives us more insight into the repressive nature of this society. It seems that sex is something to be avoided/eliminated; presumably because it may detract the young citizenry in particular from their required focus on the Party and Big Brother. Julia's sham involvement with the organization also tells us much about her character in that she is evidently very skilled in keeping up appearances. She uses her considerable involvement with the Anti Sex League merely as a front to seem like a loyal Party member, whilst actually having no belief in their ideals at all.