The Spy Who (I Thought) Loved Me

Can you imaine discovering that your best friend for years, with whom you shared milestones of your life, was in fact a traitor and a spy?  Some time ago, the news covered the case of Ana Montes, called by CNN "the most damaging spy you've never heard of", but less known is the story of Marta Velazquez, the recruiter who introduced Ana Montes to the Cuban government. Marta's dear friend Ambassador Liliana Ayalde had no idea of her friend's duplicity until Marta fled to Sweden.  Who was Liliana's best friend Marta?  Why was she spying?  Was she ever truly a friend?