Here's how it happened:
* In Catching Fire: Madge, who was Katniss's close friend and the daughter of the mayor of District 12, gave Katniss the mockingjay pin that would become a symbol of rebellion.
* During the 75th Hunger Games (Third Quarter Quell): Madge was part of the group of children who were selected as tributes. She was killed by the Capitol's forces when they attacked the rebels trying to rescue the children.
Madge's death was a tragic loss for Katniss and a turning point in the rebellion. It served to further fuel Katniss's anger towards the Capitol and her determination to fight for freedom.