Q:

Story where human response to alien invasion is organised by betting

I read this about 8 years ago I believe. 
It was set in the not too distant future and involved alien ships arriving at regular intervals. Combat teams were sent up to board and destroy the ships, but each one adapted to how the previous ones had been destroyed. One of the main characters was selected for training due to her performance in a computer game, other characters influenced the teams behaviour via gambling/stock exchange like boards.
It was written in English and I believe is was novella length.

A:

I think this is Earthweb by Marc Stiegler, which was also the answer to Alien attack novel, a team of humans are sent on a suicide mission with every human on earth to direct them.
Five alien ships, Shiva 1 to Shiva 5, attack the Earth and are destroyed in turn. The betting is done by a character called The Dealer:

So the Dealer had bought the easy forecasts. There wasn't a lot of money in it—the ninety-eight percent odds favoring Shiva V against the Fleet had meant that the hundred yen he'd put down only repaid one hundred two—but he'd won reliably nevertheless.

While the girl who was selected because of her skill with video games is Jessica:

In general, Jessica thought video games were boring. She'd played socially a few times with friends who insisted that she try the newest and greatest. But then the Boyfriend from Hell changed all that four years earlier.
  Dmitri had introduced her to Angels' Gambit . She'd played it off and on ever since, her play fiercely intense in the last few months since Earth Defense had detected Shiva V two light-days from Earth. In the last week she'd played Gambit every night after work. And now she understood why. Here in the cocoon she could look Shiva in the eye and make a difference. Tonight, she thought, she might  even win.

