John and Sophie were so frustrated with their life that they decided to end the misery by ending their life. They decided that both will jump off the building on the count of three. They started counting and on the count of three, John jumped white Sophie did not. She watched John fall off for around seven seconds when the parachute opens.

Who betrayed whom?

John betrayed Sophie.
Sophie may not jump because of the survival instinct and therefore can be given a benefit of the doubt, whereas John having the parachute seem a well-thought plan.