Ella is involved in the quest Dissent.
After Hawke and Anders follow Ser Otto Alrik into the Gallows Dungeon, they will find him threatening to turn Ella into a Tranquil. Hawke and Anders will then kill Alrik and his Templars, but after the battle, a Justice-possessed Anders will also want to kill Ella, believing her to be collaborating with the Templars.At this point, Hawke can either intervene to save her or ignore the situation (inadvertently leading to Ella's death). Either way, this event will push Anders to regain control and lead him to flee from the scene. When returning to Darktown, Hawke will find Ella (if alive) and may either convince her to re-join the Circle or return home. If the latter option is chosen, Hawke will receive a letter of thanks explaining that she either has left the Circle and is living as an apostate, or has returned to live in The Gallows.