If a reader considers the entire trilogy, I believe that Catching Fire shows the most character development and change in Katniss Everdeen. That makes sense, as it is the middle book. It serves as the bridge to get Katniss from who she was in book 1 to who she becomes in book 3. When Catching Fire begins, Katniss is essentially the same person she was in book 1. She went into the original Hunger Games to save Prim from dying. Regardless of whether or not Katniss survived, she wanted to complete that mission. Her secondary goal was to survive, herself. She managed to do that, and when book 2 begins, she is relieved at having survived the Hunger Games and is motivated to draw as little attention to herself as possible.
I mourn my old life here. We barely scraped by, but I knew where I fit in, I knew what my place was in the tightly interwoven fabric that was our life. I wish I could go back to it because, in retrospect, it seems so secure compared with now, when I am so rich and so famous and so hated by the authorities in the Capitol.
Katniss wants so little to do with the Capitol and her new status that she tries to convince Gale to run away with her. Gale doesn't agree. In fact, Gale believes in the rebellion, and he wants Katniss to help. Katniss also struggles with her feelings about Gale and Peeta; more importantly, though, she learns that she is the living symbol of the rebellion. She and the mockingjay image inspire people, and readers see in Catching Fire that Katniss is slowly stepping into the idea of taking on an intentional role in the rebellion. If she was completely against the idea of being the symbolic center for the fight, then she wouldn't have allowed Cinna to put her into a costume that transforms into a feathery mockingjay.