Based on the episode title The Crossroads of Destiny.
Everyone comes to crossroads in their lives. They are frequent and often meaningful, though only very few are such huge choices that they irrevocably change the direction of someone's life.
Even the scarred outcast of a prince who stood behind her had changed the path of his biggest regret in Ba Sing Se by joining the Avatar soon after.
She didn't even realize how important her choice was at this moment. Glaring down at the coward, rage and hate churning like the pull and push of the ocean she knew so well, Katara froze.
Swords of ice hovered in the air. All she could think about was this man and her mother, over and over in her mind's eye. It hurt. It hurt so much. She imagined killing him, stabbing and slicing him, again and again.
Though she remained ice inside, she let the blades melt into water and let the man go.
Never again would she think about killing; she started walking down the path she had chosen.