Who is Nita in the novel, Allegiant?

Nita is one of the people who live at the Bureau headquarters. She is kept there as a worker, but treated like she is inferior because she is one of the GD (genetically damaged). She and Matthew are involved. However, because she knows who Tobias is, she attempts to seduce him into joining them to help in sabotaging and stealing various lab items. Tris finds out that Nita has been meeting Tobias after hours to talk to him about taking on a mission and she tells Tobias that Nita is bad news.