Unlike the Gladers (also known as Group A) which were composed almost entirely of teenage boys, Group B was the opposite, as it was composed almost entirely of teenage girls, until the arrival of Aris Jones, the sole boy. During their Maze Trial, they escaped from the Maze three days faster and lost fewer people than the Gladers, showing that they are significantly more capable than the Gladers.
Group B's leaders were Harriet and Sonya (until Teresa joined them in the Scorch). (In the movie-universe comic The True Maze, which contradicts the original books in many respects, the group was led by Ximena until she was killed shortly before they escaped the Maze.) Several of the girls' roles seem to be equivalent to those of the Gladers, and the experiences of the two groups in the Maze appear to have been extremely similar. One major difference was that Rachel (Thomas' equivalent) was killed by Beth (Gally's equivalent), but with the Gladers, Chuck was forced by WICKED to jump in the way of the knife Gally threw at Thomas.
Before Group B began the Scorch Trials, they were told by Janson that they must kill Thomas if they wished to receive the cure when they arrived at the Safe Haven. They were allowed to travel through underground tunnels through the Scorch, while the Gladers were forced to travel overland in the burning sun. After they ambushed the Gladers, they took Thomas and dragged him up into the mountain pass, Thomas convinced them not to kill him. Group B and the Gladers met up at the Safe Haven, and they fought together against the Bulb Monsters before being rescued by WICKED.
The Maze Trial
In the story "True Maze" of The Scorch Trials Official Graphic Novel Prelude (which is canon to the movies but not to the original book series), Group B welcomes Aris to their Maze. At the time of his arrival, there are eight girls in their Maze and all are shocked when a boy comes up the Box. Their Maze is in a snowy, coniferous forested area that they call "the Spring" and refer to themselves as "Icers". Instead of Grievers, they have giant, flying, winged bat-like creatures called Shades. The Shades dwell in the outer reaches of the Maze and seem indifferent to the time of day. When the doors open in the morning, all the girls map the Maze in ice skates. At the outer reaches of their Maze complex, the maze becomes vertical, requiring the Icers to use ice climbing to further map it out.
Following Aris' arrival, the Icers, unsure of how to initially deal with him, decide to have a summit at the "Decision Tree", their equivalent of a Gathering at the Homestead for the Gladers. Whilst on his way there, Aris learns of the Icers terminology and that of the Maze and its nature. Upon arrival, the girls get into a heated debate over what to do with Aris. Ximena, the Icers' leader, is suspicious of Aris' intentions, believing him to be a spy or jynx. She cites that in the more than two years she has been in the Maze, only girls have arrived every month, until Aris. Rachel, the last girl to have arrived before Aris, disagrees. She argues that he is one of them, noting that he does not have any memories of his past before his arrival in the Maze, just like they all of them when they arrived. Alexandra, another Icer, proposes that they simply abandon Aris to the Maze and let the Shades, Group B's equivalent of Grievers, take him. Rachel and Alexandra quickly get into a heated argument over the morality of leaving Aris to die in the Maze. Before it can escalate further, Aris interjects, much to their chagrin.
Aris states that neither side is wrong in what they say. Ximena is right to not trust him over who he is. Rachel is also right in that he is not a spy and, like the girls, does not know why he is here. He nevertheless states that he is willing to assist the girls in finding a way out. The short speech earns the support of the Icers in allowing Aris to join them. Immediately afterward, Ximena punches Aris square in the face, stating that it is the most effective way of helping Aris remember his name, to which he tells them.
Sometime later, all the Icers, including Aris, head out into the Maze. Once they reach the vertical portion of the Maze, they begin the strenuous work of ice climbing it. As the girls ascend, they make note it is the farthest up they have ever been in their time in the Maze as well as the fact that no Shades have appeared. Before the group can ascend further up, a Shade attacks the group, killing Ximena and severely injuring Rachel.
As Rachel recovers from her fall, Aris discovers that there is a Maze pattern on the wings of the Shade hanged up in the hut surrounding the Decision Tree. Using their time out of the Maze, the two work together on examining the patterns and drawing it out on paper. Meanwhile, the able-bodied Icers continue to head out into the Maze, suffering additional losses as the Shades grow bolder in their attacks. One day, Aris decides to cut open the Shade and discovers a transmitter buried inside it. At that same moment, the remaining Icers, led by both Harriet and Sonya, confront the pair over the actions.
Aris explains to the rest he discovered what appears to be a transmitter, which could be a way out of the Maze. Before a vote could be made on whether or not they should activate it, Rachel presses the button hoping for the best. It instead releases Shades into the Spring. The two begin apologizing to the group for leading them into a trap, but Harriet stops them. She states that while the two didn't save them as they hope, they did finally bring an end to the nightmare of being in the Maze. The Icers quickly rally to attack the incoming Shades. As the Icers try and fight the Shades, the transmitter turns green and WCKD soldiers arrive to save them. The only survivors were Harriet, Sonya, Aris, and Rachel.