Katniss values loyalty almost as much as trust. In real life the two usually go together, but in the arena you often have to be loyal to someone you don't trust, and sometimes you have to trust someone you don't plan on staying loyal to. The whole notion of the Hunger Games toys with and threatens traditional ideas of loyalty and trust. The players all need allies in order to survive, but they can only hold onto these alliances for so long before they have to strike out on their own. This goes completely against the values of someone like Katniss or Peeta. In Catching Fire these two friends are both determined to stay loyal to each other even if it results in their own death.