So, apparently, they have this big battle where they kill other kids for rights to be fed and what not, and it comes down to the girl and her boy love (I wonder if they have sex before this or it's a pure love that doesn't need diddling... because then the guy is TOTALLY unbelieveable. About to risk death and not want to get it on with the young virginal chick who might have to kill you? what a douche!) and the decide no, we love each other, we won't kill each other. And so, logically, the cruel powers that be that force kids to fight for food say "OK - you both can have food!"

I mean, uh, what? The world is running out of food and this is a way of appeasing and two brats defy you?! YOU KILL THEM BOTH AND SHAME THEIR PROVINCES FOR BRINGING UP WEAKLINGS!!! Fuck... I need to be in charge of things.

Disclaimer - I don't know how accurate any of this is.

Her "boy love" is someone she is almost completely disinterested in, but since he expressed interest in her during the pre-games interview and the crowd loved it, their mentor has decided to play that angle in order to attract more sponsors.

Throughout the games she keeps up this appearance, hoping that he is killed by someone else and she doesn't have to do it herself, because 1) they are from the same district and she doesn't want to deal with having killed someone who was known by everyone she knows, and 2) he is the baker's son and once gave her bread for her family when they were starving (despite receiving a beating from his mother for doing so) and she feels she owes him for this.

At some point during the games, it is announced by the Gamer Makers that two tributes may win if they are from the same district. This allows the two to team up and put on more of a show for the sponsors. (As it turns out, the guy was being genuine the entire time and the girl was just playing along, heart broken, sad sad sad).

There is no shortage of food at all, The Capital is a rich and extravagant place with all imaginable pleasures, and each District (1 through 12) gets progressively poorer. The Games only exist as a means for the Capital to express their dominance of these Districts, and a reminder that they had completely destroyed District 13.

Once it is down to just the two of them, it is announced "Sorry, we checked the rules, there can be only one." The girl wants to stick it to The Capital, so she grabs a handful of poisonous berries and makes a show of both of them eating said berries. There has to be at least one winner, because despite their actual purpose the Games are treated as a great celebration. They also have to keep it entertaining for the people of The Capital, since it is a big TV event and the main source of entertainment, so the Game Makers announce they can both win after all.