How does John Grady convince Alejandra to see him?

What chapter are you referring to? Soon after, John Grady is invited to meet Duena Alfonsa, Alejandra's grandaunt. They play chess over tea and she insinuates that she does not want him involved with Alejandra. Still, he doesn't reject Alejandra's advances when she visits him late one night in the barn. She tells him that someone had seen him ride her Arabian on the night they met at the lake and that her grandaunt found out about it. Neither of them take Alfonsa's warning seriously, however, and they become nighttime companions, riding their horses by moonlight. She starts coming to his bunk when everyone else is asleep.