When Saki was younger, Tomiko (Head of the Ethics Committee while Saki is growing up) told her that she should become the new Head of the Ethics Committee since she is the most fit for the position in the village. Saki was even already learning the basics of Tomiko's technique to extend her life by studying how to piece together a broken vase with only her juryoku (Cantus or psychic power).
However, at the very end of the series, I wasn't quite sure of Saki's position/job. When she visited the bakenezumi (queerat or monster rat) museum to kill Yakomaru/Squealer, she mentioned that she had already prepared an excuse since such an action was unfit for someone in the Ethics Committee, However I think she also said earlier that the Department of Exospecies Control (or Mutant Management) had been merged with the Ethics Committee. Because/since she had already been working with that department before the attack on the village, it's possible that she is continuing her job related to exospecies while working under the Ethics Committee.
Basically, did Saki replace Tomiko as the Head of the Ethics Committee? Your answer could either be from the novel or something I missed from the show.