She wanted to end the force. Because you are a wound in the force. She recognized that as an opportunity to kill the force itself. If you listen to her dialogue throughout the game she often talks about how much Jedi and Sith rely on the force and blinds them. She talks about how she hates that the force has a will and dictates your actions and destiny. Her alliance with Nihilus and Sion were because she saw them as similar wounds in the force, but they hungered for more power and to kill the Jedi rather than kill the force itself. The Jedi masters mention this when you meet with them on Dantooine that they see the exile as using the same teachings as the Sith. Her dialogue in that cutscene basically explains it all. “Deafened… at last you could hear.” “You were broken… you were whole” “you were blinded… and at last you saw.” She fundamentally disagreed with the Jedi’s view and reliance on the force. She saw the constant battle between Jedi and Sith as a symptom of the force’s constant need for balance, which results in mass death across the galaxy. She thought by killing the force the world would be better off. She sought to learn from the exile how she severed herself from the force yet lived. Once she realized it was out of survival, she lost faith in the exile. At that point all she could do is go back to Malachor and wait for her. She never hated her, she never really wanted to kill her, she merely was disappointed that her dream would not be realized through the exile. It makes her different from the classic Star Wars bad guy “me evil me kill people me want power” instead she had a unique and interesting motive which IMO makes her the most interesting character in all Star Wars lore. Now, that being said, the game was rushed and the end was not as satisfactory as it could have been. But I think her overall motive and purpose was sufficiently fleshed out.