Born in 700 NE, she went to the White Tower in 717 NE. She retired to the country in 973 NE when Tamra Ospenya was raised Amyrlin Seat. It was speculated that she did so because of personality clashes with Tamra, and because she wanted to be Amyrlin instead.
After the death of Sierin Vayu, Marith was called from retirement to take the Amyrlin Seat. The Hall felt they had no choice, as both Tamra and Sierin had died suddenly, as had many senior sisters - part of the Black Ajah's efforts to find the Dragon Reborn for themselves.
Marith was the last of three Amyrlins to have died in a short stretch of time. After her sudden death in 988 NE, only four years after her gaining the Amyrlin Seat, she was replaced by the then young Siuan Sanche. She was also the Amyrlin who in 985 NE sentenced the Red Sitters Toveine Gazal, Lirene Doirellin, and Tsutama Rath to exile and hand labor on a farm for the role in gentling male channelers outside of the White Tower. They were publicly unseated and birched in front of the White Tower, without any explanation for the outside world.
Her death was of natural causes.
Who was the Keeper of the Chronicles under the reign of Marith Jain? It is speculated that it could have been Siuan Sanche herself, because when Seaine Herimon put her name forward as an Amyrlin candidate, she stressed how Siuan was young, had an unusual strength of character, and was also a very good administrator; although this was unknown to most sisters, Siuan ran the Blue Ajah's eyes-and-ears network, which was the largest, making her a good administrator. However, Marith Jaen was absent during Siuan's life as Aes Sedai, and thus she would not have chosen Siuan unless she was suggested by the Blue Ajah as a possible Keeper.