What is the significance of the song, Someone to Watch Over Me, in the novel, What She Left Behind?

Clara is upset when she hears "Someone to Watch Over Me," a song about love, on the radio while being driven into the asylum. This is because the song was Clara's and Bruno's favorite when they danced to it at the Cotton Club. The song's title is darkly ironic, as Clara will truly have almost no one watching over her while she's held in Willard. That is, until Bruno sneaks into the facility and attempts to free her, at which point Bruno literally is watching over Clara, trying to cause her escape from the facility.