I don't believe for a moment that this girlfriend didn't have a clue about what her killer boyfriend was planning to do.  Nobody nilly willy jumps on an airplane and leaves the country without some type of resistance or questioning why she needs to leave.  Even children, by instinct, question everything their parent(s) do.  It's human nature to be curious and resistive.  Moreover, people don't stay in a relationship for a year or more and not know something about their partner's behavior or thought process, or unless they're blind, crippled, and crazy. The girlfriend is hiding information.