Quote 1
"Oh, she jolly well doesn't see why there should have been," Fanny repeated, as though to an invisible listener behind Lenina's left shoulder. Then, with a sudden change of tone, "But seriously," she said, "I really do think you ought to be careful. It's such horribly bad form to go on and on like this with one man. At forty, or thirty-five, it wouldn't be so bad. But at your age, Lenina! No, it really won't do. And you know how strongly the D.H.C. objects to anything intense or long-drawn. Four months of Henry Foster, without having another man—why, he'd be furious if he knew…" (3.93)
Fanny's aversion to monogamy is partly due to her desire to follow the rules, but also partly a reflection of her conditioning. She has been programmed, essentially, to have an innate, visceral aversion to monogamy.
Quote 2
"Well, if that's the case," said Fanny, with decision, "why don't you just go and take him. Whether he wants it or no." (13.28)
Fanny just suggested rape, but we're thinking that, in a world where "everyone belongs to everyone else," they don't really have any notion of what this means.
Quote 3
"And then he spends most of his time by himself—alone." There was horror in Fanny's voice. (3.128)
What begins as Bernard's defining feature is both a virtue (it makes him an individual) and his downfall (it makes him insecure, which makes him manipulate John, which makes him famous, which makes him petty…).