<old witch mode on>
Ah, Dark Jedi. Already you presume much. Perhaps she became a Sith Apprentice out of necessity, to prevent a greater evil from being unleashed upon the already fragile Republic. Her mission was simple - to make Malak feel like he had won, to make him feel safe - and at the same time, allow Revan to finally bring an end to the Sith crusade he started. Have you never wondered why Dodonna never mentioned the losses suffered because of her Battle Meditation? There virtually weren't any, and this is another pleasant sign of benevolence towards the Republic we should thank Bastila for. And perhaps the dark side, which could never completely consume her, had no power over her whatsoever, and Malak's skills of conversion and persuasion, which proved so effective during the Mandalorian Wars, finally came to a failure, and the young Jedi who did not follow him to Malachor chose not to follow him into the darkness. But you know this. The visions of Korriban are not easy to forget, and they echo within you still.
<old witch mode off>
Actually, that was one moment in the game that was, to some extent, predictable. Not fo r me, because KOTOR was the first true RPG I ever played, but for others... for whom the name Aribeth de Tylmarande does bear some significance.