Yellow Victory Dress

The Letter Y Chapter 26: The Yellow Dress

"Venia helps me into a pair of flat leather sandals and I turn to the mirror. I am still the 'girl on fire.' The sheer fabric softly glows. Even the slightest movement in the air sends a ripple up my body. By comparison, the chariot costume seems garish, the interview dress too contrived. In this dress, I give the illusion of wearing candlelight."

The Capitol is furious about her showing them up in the arena. They can't stand being laughed at and being the joke of Panem. It would've sparked an upheaval in the districts of Panem had they both wound up dead. There had to be a victor and the gamemakers decision to reinstate the previous rule that "two tributes from the same district could live" was a good call.
Here's what she was supposed to say to avoid any trouble. I was madly in love with him, and the thought of living without Peeta was impossible to bear. Love made me do it.