Anita was a human member of the archaeological crew that came to the Library in the 51st century.
When Miss Evangelista was killed and the crew listened to her data ghost, Anita recalled her grandfather's data ghost, who had kept talking about his shoelaces. (TV: Silence in the Library)
Along with Proper Dave and Other Dave, Anita was eaten by the Vashta Nerada. Because the Tenth Doctor had turned her space helmet dark, River Song and Strackman Lux thought that she was still alive. The Vashta Nerada had also learned to speak using her voice. The Doctor realised she was dead because she only had one shadow after the Vashta Nerada were attached to them. He kept the knowledge to himself in order to use it against the Vashta Nerada.
In confronting the swarm of Vashta Nerada, the Doctor told it he had really liked Anita, commenting, "She was brave even when she was crying, and she never gave in." Her death moved the Doctor to be angry and forceful in his demands to the Vashta Nerada. She was returned to life in the computer core after CAL and Doctor Moon had saved her and the rest of the team. (TV: Forest of the Dead)