What do we learn from the actions of the character Isa bel Baldwin (The narrator´s wife)?

We learn that she understood and supported Sonny's love for music, at least until he started skipping school. Soon after, Sonny joined the military. Isabel does note, however, that living with Sonny wasn't like living with a person, it was like living with a sound..... that he was wrapped up in his own world and unreachable.