In the beginning of the book, Esperanza isn't quite ready to emerge into asexuality. She is completely ignorant towards the whole idea of sex.
When she becomes an adolescent, she begins to experiment with the power she has against boys. She gets taught the fundamental facts about boys. She plays with the idea that physical beauty could help her escape from her surroundings.
By the end of the novel, Esperanzas views pn sex has evolved, and she rejects sex as a means of escape.