Thread:Inept Wiki User/@comment-5275759-20200523162949/@comment-25431873-20200907155639

In Railgun episode 21, Therestina says that people are surprised that a woman such as her likes innocent things like the animals decorating her room, which not only calls her a woman, but clearly implies this isn't something for someone her age and is too childish. Later in episode 24, she is constantly called "that woman" and constantly calls Mikoto and co. "schoolkidd" and later says that of all espers in AC.

So in several instances she makes a distinction between her as an adult and the students and espers of the city. It's not explicitly said, but I feel that based on these words, her design, and her position, it is fair to say she is intended to be read as an adult.