Who is La Comtesse Teresa di Vincenzo (Tracy) from On Her Majesty's Secret Service and what is their importance?

La Comtesse Teresa di Vincenzo is the beautiful and tragic daughter of an English governess and the head of the French mafia. At the beginning of the novel, she is suicidal. After her mother died, Tracy began partying with the idle rich. She married a count who ran off with her money and left her with a child. She seemed happy for a while until her child died of spinal meningitis.