LitCharts assigns a color and icon to each theme in The Sun is Also a Star, which you can use to track the themes throughout the work.
Immigration and the American Dream
Passion vs. Reason
Interconnectedness and Destiny
Isolation vs. Connection
Summary
Analysis
Natasha tells Daniel that he should go. She asks him if he's thinking about her at all, and if he's at all curious about her life as an undocumented immigrant. Daniel looks guilty, and Natasha tells him to follow his own advice and tell his parents he doesn't want to be a doctor. Daniel quietly says it's not that easy, but Natasha ignores him. She says that she hates poetry, but she once read a poem that said that you can't make a home out of human beings. Daniel says nothing. Natasha says that Charlie was right: they can't be together, and he doesn't love her. He just wants to someone to save him, and he needs to save himself.
Now that Daniel has turned on Natasha, it reinforces her initial worldview that the only safe way to move through the world is alone and isolated. This again shows that isolation is a coping mechanism for her because she doesn't believe that people are actually trustworthy. Daniel's silence suggests he knows he's wrong to blame Natasha, though the connection she makes to Charlie just adds insult to injury.