Lavinia is an Avox girl who worked as a Capitol servant for Katniss before the 74th and 75th Hunger Games. Throughout The Hunger Games and Catching Fire, she is known simply as the "Avox girl". Later on, Peeta announces her name is Lavinia.
Before she became an Avox, Lavinia and an unknown boy, whom Katniss believed was her brother, were seen by Katniss and Gale while they were out hunting, in an off-limits wood in District 12. They appeared to be escaping from the Capitol, as Katniss noted that the two had a "Capitol look" to them. A Capitol hovercraft appeared; the boy was struck with a spear and killed instantly. Lavinia, however, was scooped up by a net and taken into the hovercraft, she briefly locked eyes with Katniss and Gale. When the boy was killed, she let out a scream, and Katniss wondered if it was her last.
Years later, Lavinia waited on Katniss as an Avox whose tongue had been cut out for committing crimes against the Capitol. Katniss said she knew Lavinia. This worried the residents from the Capitol, so Peeta stepped in and claimed that Lavinia looked like Delly Cartwright - a girl from District 12 who went to school with them. As an Avox, she could not publicly acknowledge anything that was not a direct order, so Katniss' initial attempt at conversation was ignored. However when she later walks in on the mess Katniss has made in her room prior to interview night she shows some response to Katniss' attempted apology, indicating by gestures that Katniss did not need to be sorry, and that there was nothing she could have done.
During the Quarter Quell, Lavinia was once again Katniss and Peeta's Avox, this time alongside former Peacekeeper Darius, old friend of Katniss. In Mockingjay, it was revealed by Peeta that the Capitol had tortured Darius and Lavinia to death during interrogation. Since the Avoxes were unable to speak or answer questions, Peeta believed they were tortured simply so he could be forced to watch. Lavinia died more quickly than Darius because they used too much voltage when shocking her and her heart stopped immediately.
Lavinia has dark red hair, striking features, and porcelain white skin. Being an Avox, her tongue was cut out and she is therefore mute. She is also subject to a lifetime of servitude to the Capitol. As an Avox, she is of Panem's lowest social class, essentially a slave.