Elia is an Erudite-born girl, who is too young to have officially chosen a Faction. She has short, black hair and is around ten or eleven in Insurgent. She is very intelligent, but also more child-like than grown-up Erudites.
In Insurgent, she left the Erudite faction and went to stay in Amity with the other Erudites who did not agree with Jeanine Matthews. She helped create gadgets to use in the fight. She likely didn't go back to Erudite to try to retrieve the video of Edith Prior because of her age. Her fate is unknown.