In Chapter 13 of Brave New World, what makes John change his mind about Lenina?
Ever since he has met her, John the Savage has been totally in love with Lenina Crowne. But his love for her is the sort that puts her "on a pedestal." He thinks of her as perfect.
Because of his values, he thinks a perfect woman must be a virgin and must not have sexual desires (or at least not show them). He is very old-fashioned.
Meanwhile, Lenina isn't in love, but she thinks John is really attractive and wants to sleep with him. In her apartment in this chapter, Lenina takes off her clothes to have sex with John.
When John sees this, he starts to think she is a whore because that's what his values say she is if she acts like that.