As Katniss heard her sister's name she felt like just going up there and saying..." NO! I want to go." But she couldn't. She didn't have the strength. So she just let Prim go.
After Prim had said her goodbyes to Katniss, she just left. On the train. On the train of sorrow. Maybe this is the last time she would see her sister. She regrets her decision.
A few days later they were waiting for Prim's training score. Katniss had low expectations for her sister. But somehow she pulled off a 10! But this makes it worse. This makes her tuff competition.
Day by day they saw their little girl, Prim, battle and survive through the days of these weary Hunger Games. Until, the last day. It was just her and a boy she had never seen before named Cato. Suddenly a stampede of mutts came tumbling in and then, Prim instantly noticed the eyes. She knew what they had done.
Soon after a mutt with bright blue eyes pounced on Prim. That was the end. For Prim. The end of Katniss' hope. Gone. Forever.