In the book, as Atanna slowed Kentril's fall to the earth, thus saving him, Kentril sees her as she "faded away"when touched by the sunlight. This is unusual because all other denizens of Ureh had been burnt away in their zombified forms(when touched by the sunlight). To me this suggests that Atanna's sins have been forgiven by the heavenly forces and instead of her soul being damned to hell or, as the previous writer of this section had suggested, she revert to being stuck in limbo again (which would have been a hellish punishment in solitude). Her good deed in not outright killing Kentril when he tried to sieze the crystal and then her saving of him by not allowing him to fall to his death caused her to deserve forgiveness. She may have gone to Heaven. It at least seems that it was anything but Hell.