Summary:

I believe that the "mental rating" is actually the evaluation for the degree for acceptance of the society. The society doesn't only means its politics, sciences, or economics, but also normal people and communities, which are part of the community. Citizens of the Watcher's society may have higher mental rating due to physical or mental illness, temporary downfall, or conflicts with the community. This brings us to the ultimate question of why Ava's mental rating is healthy throughout the plot? She was the one who challenges the system in front of the system itself, how possibly that her mental rating doesn't waver? It is important to recognize that she doesn't deny the working and the benefits of the system even till the end. She strongly believes that the system brings happiness, peace, and stability, which is shown by he dedication to her career and her friend's satisfaction. Nevertheless, she still insists that changes are needed. Her thirst for change intensifies as the plot progresses with different stories showing problems and flaws in different aspects of the society. It is noted that what she wants are improvements, not a complete abolishment. Therefore, the system recognizes her thoughts as not only beneficial to the society, but also beneficial to the system itself, leaving her aa clean and virtuous mental rating.