My take on Avox girl.
Beauty
By Capitol standards, Lavinia is a beauty, definitely a beauty. She's lucky enough to have good genetics in the first place, and with all softness and care of the Capitol, it's enough.
Of course, she can't compare to Cashmere or even Gloss crammed into a dress. That doesn't matter though, because they are from District 1 and Lavinia's from the Capitol; there aren't any district-Capitol contests anyway. Besides, the siblings aren't even around 24/7/365(366).
Why We Need It
Lavinia has an uncle who's an escort, and when she was little he used to tell her stories about the tributes that he had to oversee. They were, for the most part, starving children that ate like black holes or vacuum cleaners. Many of them were also pathetically weakened by horror of being reaped, but they still whispered about the horror and shallowness on Capitol streets.
In response, Lavinia was pouting, or maybe she' feel contempt, because to the districts, the only thing you need in life is to escape punishment and eat. To escape punishment, it's work. To eat, it's to work and earn money to buy the food you eat. And the Capitol is above that, so they have better things to do. Like give their eight year olds injections of poison just for the removal of dimples, burn their eye brows off, and other things like that.
It's all in good, so there's really nothing to be said. In the Capitol, there are rich people, and there are poor people, but everyone still gets along all right economically. It's your beauty that changes things. Beauty makes that rich lecher want to marry you and shower you with money that you collect as much of before you're replaced. This whole policy probably explains the hordes of pastel-colored or neon-colored blimps walking everywhere.
As you can see, beauty is a hard affair.
The Secret
Once Lavinia meets Cashmere and Gloss when she is 14 or so. The Games had already started, and the sponsoring had started.
Usually, you modify your body when your parents schedule an appointment for you. Most of the time, that's when you're 5, or 6. Generally you get a tattoo. When you actually remove chunks of meat or cut yourself, you're around 15.
Lavinia hasn't started really, because she likes being unique, and one way to be unique is to be digestible by the tributes and district people while still holding your own. She, frankly, doesn't need it as much as some of her Capitolian acquaintances, and she knows that.
"I'd like to sponsor the female tribute Twinkle," Lavinia says. Her dad had just made a huge bet on said tribute, and part of the conditions was, "No sponsoring". Lavinia is a way of cheating.
"All right," says Cashmere. She conducts the transaction, and there. It's done.
"You don't look like many people in the Capitol," remarks Gloss.
"She has the Capitol air," says Cashmere.
"I mean your traits."
"Well…I didn't start accessorizing yet," Lavinia explains.
"I see. If I were you, I'd make sure it stays that way, as much as possible." Gloss seems to be thinking about how to word something. "The best type of beauty is classical. That's how Cashmere and I survived so long."
Lavinia decides that there is a lot of sense in what Gloss said. Because the Capitol, after all, is a candle burning on two ends. You might get some painful surgery that gives you bunny ears, and all you get for the pain is being left behind.
A few years later, she notices a few wrinkles here and there, but poisonous shots that paralyze her face with poison are all she needs. And they're the only cosmetic she'll use if she can help it.
Marriage
When Lavinia is 20, her family decide that she is ready to be married. In the more economical parts of the Capitol, the average marriage rate is somewhere around 27, but the richer people haven't gotten the message and they marry like the districts: young.
Most of those marriages are arranged, and families interchange social status for money and love for pride. See, half of these marriages ends up with the husband having mistresses, and the wife buying victors, and their kids being raised up by a nurse. If there are kids.
Lavinia at least gets someone she calls 'friend'. He's known Lavinia since they were little and they have some kind of like in between. If they pretend they're roommates with a closer bond, life will be fine.
The wedding is very grand, and the bride and groom still have to be deflowered. (Lavinia isn't chaste because she likes being pure; it's simply that there's a risk of conception and she doesn't think she's ready for children.) There's a few hundred people dressed in finery, and the celebration is four days long. Escorts are invited, Gamemakers are invited, and pretty much everyone the groom's mother knows is invited.
Bored
Normal Capitol girls have a mission to make themselves at the top of fashion, and the normal Capitol guys have to support their wives' missions and still make money for life. Lavinia and her husband don't really have that type of system, because all the wife wants is a few shots for her wrinkles sometimes, a brush, slight make up, and other moderately useful grooming tools. Besides, they are rich, so even if Lavinia was a fashion light, her husband doesn't really have to work that hard.
Which leads to the stage: boredom. Not with the spouse (well, maybe, in a way), but with your overall life.
Lavinia and her husband both wanted something to do that taxed them. Too bad, the Capitol isn't supposed to be taxing.
"Vinny?"
"Yes, Aeneas?"
"I'm thinking…What would be fun? Like the quests we used to make when we were little. That kind of fun."
"Let's go on another quest then."
"To where?"
"I don't know."
Aeneas pulls down a map of Panem. There was region in the way east, where no one lived…
Plan
First, Aeneas researches the trains that pass through Panem, and find one that goes to Twelve. It might be too short though, so he looks for an alternative route to Twelve that's going to take more time. Aeneas confers with Lavinia, and they finalize the route.
Second, they buy two tickets to the arena furthest away from the Capitol. It will be their alibi.
Third, Lavina begins to pack their supplies: victuals, a change of clothes for them each, lots of money, and some disguises.
Fourth, they plan the date.
Truth
The journey isn't some little kid's quest, and Lavinia and Aeneas find out after one-fifth of the route. But they asked for this, and they stick with it.
Search
Aeneas' mother finds that her son and daughter-in-law are missing.
The whole Capitol searches for them, and there is a clandestine Peacekeeper report about two youngsters that suit the description. A hovercraft is sent out to punish them, because Capitolians would do well to stay out of the districts, or they may feel pitiful and spread the news, and then the system would come crashing down.
Caught
Lavinia and Aeneas are in District 11 when they see a hovercraft stare at them. It's definitely from the Capitol; the 11 people use oxen, not personal floating devices, to farm.
"Run," Aeneas whispers. He doesn't have to say that, because the duo are already sprinting. But a human sprint is no match for a hovercraft, and they are caught.
Result
Aeneas is killed. Right away. Lavinia is taken back, and the Capitol is told that both Lavinia and Aeneas are dead, their bodies not found.
There's enough people in the Capitol who recognize Lavinia, and so she can't do anything public. They find an Avox role for her in 12, and the former escort is replaced with a snap of fingers.
Epilogue
From what she hears, there is a volunteer from Twelve this year, and that's very rare. Lavinia has to serve her, and she can't help feeling pity and contempt for the coal miner's daughter, because the poor girl probably doesn't know that like finding Thirteen, winning the Games is not as grand as it seems.