What does the song "I'm Alive" relate to in Act 1, Scene 8?

Diana answers Dr. Madden's questions, but then stops when he starts asking about Gabe, who appears and sings the edgy, rocking "I'm Alive" about the intensity of his presence in Diana's life. His song is intercut with dialogue between Dan and Natalie in which they discuss how Gabe's presence is never going away and Diana is never going to get better.