Masha Lutz

Masha Lutz was the daughter of Mariska and Samuel Lutz. She was most likely born in Rapture, judging from her mother's comment that she'd never seen a tree before coming to Arcadia.

During the Rapture Civil War, she was taken by Andrew Ryan's men and turned into a Little Sister. Her parents held out hope that she would find her way back to them. One day, however, they saw that she no longer recognized them, most likely due to Suchong's conditioning. They commited suicide in despair.

Earlier articles mentioned that the Big Sister was "someone with a history in Rapture" Masha Lutz is the only Little Sister mentioned by name, therefore, it might be her.