What is revealed in the conversation between Henry and Natalie in Act 2, Scene 12?

Scene 12 - Natalie joins Henry ("Hey #3," "Perfect for You - Reprise"), revealing her pretty blue dress. Their sung conversation reveals that Henry thought they were through, and that Natalie fears she'll end up crazy like her mother. When Henry says he'll be there for her, she protests, with increasing anger, that she might turn out to ruin his life.