Both Winston and Julia, of George Orwell's 1984, state that the only betrayal would be for them to not love one another. For them, regardless of anything else that they do, as long as they love one another no betrayal is committed.
Able to stay committed to Julia through the first two stages of his "regeneration" (learning and understanding), Winston betrays her in stage three: acceptance. Winston's betrayal accompanies his exclamation of "Do it to Julia! Not me!" It is here where Winston loves Big Brother over Julia.
As for Julia, she is also broken by the Ministry. She is far easier to break than Winston (given Winston planned to fake his love of Big Brother, yet keep his love for Julia).
Therefore, given that both Winston and Julia both loved Big Brother, each betrayed the other. They both even admit that they have betrayed each other when they see each other after being released from the Ministry of Love.