She is described as being a large woman with broad shoulders and well muscled and so she looked as though she had worked a hammer or a sword.  But she is not fat.
Her personality is in accordance with her body type: direct and forceful, sometimes overpowering.
Strength and Abilities
In "The Wheel of Time Companion" her level of strength in saidar is described as 29(8) but it is a mistake because such level does not exist, it could be either 20(8) (most likely) or 29(17).
Magla is 161 years old. She was born in the year 839 NE and went to the White Tower in 854 NE. After spending seven years as novice and seven as Accepted she was raised to the shawl in the year 869 NE. She bonded Rorik as her Warder before becoming Sitter.
She was elected as a Sitter for the Yellow Ajah in the year 985 NE.
Becoming a Sitter in Salidar
In the year 999 NE after the schism, Suana Dragand, First Weaver of the Yellow Ajah, ordered Magla to join the rebellion to control and defuse events. This was also done for her safety, as she was not invited to the vote to depose Siuan and raise Elaida.
In Salidar she apparently allied with the Rebel Aes Sedai and was elected again as a Sitter in Hall. Apparently, she is strongly allied to the other powerful Yellow Sitter Romanda Cassin and follows her lead in the Hall.
In reality Magla had a difficult time going against Romanda in any way, but since following Romanda helped counter Lelaine, and usually resulted in stalemate, she did not try very hard. Nevertheless Magla was able to favour the election of Salita as third Yellow Sitter against the will of Romanda, who was supporting Dagdara, but also herself for the chair and the position of Ajah Head among the Yellow rebels.
Magla is one of the Aes Sedai who misses Nynaeve al'Meara Healing of both Leane Sharif and Siuan Sanche from Stilling. She insists on going through the process again step by step and even tries to give advice on how to improve it and how to make Nynaeve angry again so she can keep channeling. She even fights with Larissa Lyndel and Zenare Ghodar to have Nynaeve show her first.
War against Elaida's White Tower
She votes NO on the Rebel Aes Sedai declaring war on Elaida do Avriny a'Roihan and is outvoted. She is one of the Sitters that want to begin negotiations with Elaida and is part of the group that negotiates with the White Tower Aes Sedai in Darein.
She is also part of the group who question Shemerin about how she escaped the White Tower.
Black Tower Alliance
When the proposal of an alliance with the Black Tower is laid before the Hall, she becomes furious, calling Moria Karentanis a Darkfriend and almost comes to blows with her over the issue. She subsequently votes NO in the Rebel Hall of the Tower for an alliance with the Black Tower.
Magla remains a Sitter when the Hall of the Tower is re-united after the White Tower Schism. The Sitters try to hold a secret meeting without Egwene, discussing ways temper the Amyrlin's power when a declaration of war is called. Magla voted for a proposal that would allow only Egwene to deal with the monarchy of the world, which includes Rand as he is King of Illian, while the Hall would take over prosecution of the war and deal with Gareth Bryne's army.
In that same meeting, Magla voted in favor of the new rules and procedures in the Hall, which included temporarily replacing a Sitter when she is absent from the Hall and that no meeting of the Hall can commence without all Sitters and the Amyrlin Seat being present.
While the other two Yellow Sitters (Romanda and Doesine) fought and died during the Last Battle, Magla instead helped Rosil to manage the hospital in Mayene, and to rule the other Yellow Sisters, the Accepted and novices relocated there for safety.