Not necessarily, the younger a peraon is, the more amazing their actions seem if those actions are considered "mature" or "smart". The older that child gets, the more typical those same actions will look when compared to their age. Also, she has very little chance to grow mentally beyond reading and when she disobeys and ventures out of the demon sect. A good example of this is seen in how it took her some time to realize the bad ways of the other kids at the tournament. Lack of exposure can be hindering. I feel like as a little kid she was known for intelligence but as the story progresses it will lean more into her being more of a "martial arts" genius then an academic one.
Is it just me or did the mc become dumb? She was supposed to be amazing