How has Christina's impression on Jacob changed ?

They start to talk about Christina and Michael. Michael tells Josie their story. They were next door neighbors, and fought constantly until they were 16, when told each other their problems and became best friends. After a while, those feelings morphed into something more, and they had sex, which Michael regrets. Not because of Josie, but because he thinks they weren’t emotionally ready. Still, he believes it was worth it, because they have Josie now. Josie asks if Michael has a girlfriend, and when he says he does, she tries to make him jealous about her mother. Josie says Christina is dating an Italian man, and she (Josie) adores him, but that she likes Michael better. This makes Michael smile so beautifully that Josie begins to love the idea of him being her father. Michael in return says that if he had to choose a daughter, he would have chosen Josie. The pair continue to banter back and forth for the rest of the ride.