The hugely popular science fiction novel by Orson Scott Card is set in Earth's future, a future that has seen war with an extraterrestrial species formally called Formics and popularly known as Buggers.  Expecting another war against these aliens, an international space military foce recruits the best and brightest children from all over the planet to train them as eventual military leaders.

In addition to The Help, Davis is also currently appearing in Extremely Loud & Incredibly Close.  You'll also recognize her from Doubt, Disturbia, and Eat Pray Love, amongst her many other credits.  

According to Variety, Davis is on board to play "a military psychologist who oversees the emotional welfare of the young trainees in Colonel Graff's military program. She also helps design the games that test their skills and resilience."

It's been a while since I read the book, but I don't remember this specific character, and I suspect she's may have been invented to provide an external voice to the protagonist's struggles, so much of which are wholly internal.  She could also have been created at partially from the vague dialogues between Colonel Graff and an unspecified character that open each of the novel's chapters.

Hugo star Asa Butterfield is set to play the title character, Andrew "Ender" Wiggin, the most promising student at Battle School, the orbiting military academy where most of the action takes place.  His Hugo co-star Ben Kingsley is also on board as military legend Mazer Rackham, while Harrison Ford will play Ender's hardassed kinda-sorta father figure, Colonel Graff.  The former actor has won an Oscar, while the latter has been nominated, as have supporting players Hailee Steinfeld and Abigail Breslin, playing Petra Arkanian and Valentine Wiggin, respectively.

Gavin Hood is directing the film from his own screenplay.  The South African native gained international acclaim with Tsotsi in 2005, then followed it up with the drama Rendition and went into event movies with X-Men Origins: Wolverine.  Ender's Game is produced by Odd Lot Entertainment, Digital Domain (also providing visual effects), and Star Trek screenwriters Roberto Orci and Alex Kurtzman.

Ender's Game is scheduled to finally arrive at a theater near you on March 15, 2013.