What does Rose's codename, Viola, symbolize in the novel, Warlight?

The codename Viola symbolizes the fractures and division caused by Rose’s espionage work. While working as a spy, Rose essentially had to take on a new identity, and this identity committed many immoral acts, from marital infidelity to the enablement of large-scale military massacres. Rose was essentially unable to revert to her old life, as the enemies she made as Viola disrupted her old life and eventually killed her.