Given Isla's extreme curiosity about his other lovers, Adam was forced to tell her about everyone he was fucking other than Leila and Xu Lin.
But she was not satisfied with just their names; she wanted to know how he met them, how he seduced them, and what his reasons were to choose them.
He spent the entire ride back talking about those things; some interested her while others didn't so much, but she did take great interest in Joe and his family and how Adam wants to mess with him for being a pathetic leach of a friend that he is.
Hearing how this Joe character mistreated him, Isla got furious and wanted to get involved, which made Adam laugh, but he told her he would deal with Joe all alone.
Adam realized that Isla was taking the role of his first girlfriend far more seriously than he expected; she was going out of her way to learn about his other lovers, and when he asked why she was so interested, she said it was to maintain harmony among them.
