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Sonya is the second in command of Group B along with Harriet, another Group B member, in their Maze. She is the younger sister of Newt. Her real name before being taken by WICKED was Elizabeth, or Lizzy for short. Her role in Group B seems to parallel that of her brother's.
In the prologue of The Fever Code, a young Lizzy is living with Newt and her parents in a basement. WICKED has somehow become aware that Lizzy is Immune, but her parents have refused to give her up. WICKED agents force their way into the basement and demand that Lizzy be handed over to them. Her dad shoots one of them in the leg, but a woman pulls out her own weapon and shoots both him and Lizzy's mother dead. Someone says that Newt could also be useful as a control subject. Newt hugs Lizzy tightly as they are both taken away.
Lizzy is put in Group B and renamed Sonya. She is not allowed to see her brother, but unbeknownst to her, Newt often sneaks around at night and spies through a window into her dorm, making sure she is all right. When she is twelve years old, Newt, with the help of Thomas, manages to enter her dorm through a secret way and say goodbye to her before he enters the Maze. He cries, wondering why WICKED keeps them apart, and Lizzy tries to comfort him, saying that as the older one, he should be comforting her.
In The Death Cure, though never directly confirmed, Sonya was given back her memories. This is based off the fact that she was assigned to one of the rooms with Aris and a couple of other Gladers to remove the Swipe. Sonya helped Thomas and the others lead the Immunes out of the Maze and through the Flat Trans to get them to the Safe Haven. She escaped to the Safe Haven along with the rest of Group B and the Gladers.
In Maze Runner: The Scorch Trials, Sonya, Harriet, and the other members from Group B were placed in a separate WICKED facility. While investigating the harvesting room, Aris and Thomas overhear Janson conversing with Ava Paige, who reveals that The Right Arm raided WICKED bases and facilities, one of which is likely the location Harriet and Sonya were housed. She sneaks up on the ragtag group of Gladers, Jorge, and Brenda with Harriet, holding them at gunpoint. She orders the Gladers on their feet from their hiding places behind abandoned cars and freezes when she sees Aris traveling with the group. Overjoyed, she embraces him, relieved to see him alive.
Sonya, Harriet, and Aris catch up over dinner, talking about their escapes. When WICKED raids The Right Arm base, she fights alongside the other Right Arm volunteers to defend it. Eventually the WICKED forces overpower The Right Arm and force everyone in lines. Sonya is roughly shoved to her knees in a line with Newt, Aris, Minho, and Harriet before a WICKED soldier scans the tattoo at the back of her neck, calling out "B4." Ultimately, she is taken captive by WICKED along with Aris, Minho, and some of the other Immunes.
In Maze Runner: The Death Cure, Sonya is among the Immunes rescued by the Right Arm when a team led by Thomas and Vince assault a WICKED train and bring the cart she and other Immunes were on board back to their new hideout. She later escapes to the Safe Haven, along with the rest of the survivors.
Appearance and personality
In the books, Sonya is described as having reddish blonde hair and very pale skin. In the film, she has light blonde hair in a side braid and hazel eyes, portrayed by Katherine McNamara.
As a child, Sonya loved her older brother very much, and he was very protective of her. Later on, when she was twelve years old, Newt said goodbye to her before going into the Maze, and Sonya ended up being the one comforting him that time.