Nola is first encountered in the Moonrise Towers throne room, standing guard over the trial presided by Ketheric Thorm. After the trial ends, Nola moves over to stand guard on the western side of the room, next to the door leading into the Moonrise Towers Prison. Interacting with Nola will have her show the party indifference, and not care about their status as a True Soul. Nevertheless, after Isobel is kidnapped, she confidently asserts that she'll become a True Soul once they take Baldur's Gate.
Defending Moonrise Towers
If the Nightsong is freed and the Harpers launch their assault on Moonrise Towers, Nola will be part of the remaining forces defending Moonrise Towers, and can be encountered in the throne room. Should the party enter the throne room prematurely, or kill a few Absolutists in the hall, she will join combat.