In 1984 how does Julia’s note telling Winston she loves him transform his impression of her?

In Chapter 1 of Book 2, the dark-haired girl to whom Winston had taken a strong dislike surreptitiously hands him a note that reads “I love you.” Winston believes she must mean it and that she is not using the note to entrap him, “because of her unmistakable agitation.” The note directly causes Winston’s feelings for the girl—whose name he still does not know—to change completely. He goes from disliking her to trusting her completely, and eventually he falls in love with her. The word love is from a time gone by, when “there was still privacy, love, and friendship.” When the dark-haired girl uses this word, it means she is guilty of the same rebellion that Winston feels growing within himself.