Andi (who normally speaks with a Sloane RangerLondon accent) briefly imitates the accents of her Alabaman roommate Jennie and New Englander best friend Bell in Part 5, when they're testing her memory by asking her questions about things they said to her.
Part 5 also reveals that Jennie has been imitating Andi's Sloane accent on occasion; she does so twice during that chapter.
When Andi speaks to two Quebec natives in Part 9, she imitates their accent as well, though she is new to French at the time.
Andi: So, want me to write a computer program for you longhand? Best to give me a topic — I couldn't think of one. I'm not entirely sure what people write computer programs about. The book suggests it should just output 'hello, world,' but I’m not one to make that kind of unambiguous welcome to a planet I've barely even seen before.
Dream Land: In Part 5, when Andi goes to sleep at the end of the day, she discovers that she is alert and conscious as the normal dream processes of her brain are operating — looking around in a landscape full of mirrors reflecting the events of the day, her mental connections to those events, and at least one visitor from outside her mind stopping by to check her out.
Insistent Terminology: Andi constantly has to correct people calling her "Ms. Gannett" or "Ms. Moore" instead of "Ms. Gannett-Moore". She even ends up doing this in French.
Bell: I mean, on the big list of problems–- Andi: Yeah, you're right. Because if there's anyone in public school who really gets on well — really has a wonderful time for all the years she's there, it's the know-it-all. Well, know-it-all-except-for-why-it's-happening.
Only Known by Their Nickname: Her full name is "Andrea". The only people who use it are professors and administrators, and even then only when she's in trouble — everyone else calls her Andi.
Parental Abandonment: Andi's parents are essentially non-entities in her life — sending her from boarding school to summer camp to summer camp to boarding school essentially continuously.
Powers That Be: Discussed in Part 6, where Tatum says that there aren't any secret world-controlling superhuman conspiracies now....
Super Intelligence: Andi appears to have spontaneously developed the ability to answer any question given sufficient information — an ability she first demonstrates when she (previously a mediocre maths student) solves thirty binomial-multiplication questions on an algebra test as quickly as she can write.
Good with Numbers: Including being able to rattle off the cube root of 897 to eight decimal places as fast as speaking.
Instant Expert: In Part 3, she figures out how to play the guitar like an expert in minutes, just larking about.
Photographic Memory: She also perfectly recalls everything that she ever observed, running uninterrupted backward in time as far as the surgical operation meant to give her powers when she was three years old.
Super Speed Reading: In Part 4, Mr. Stone tests this ability by handing her a book of Shakespeare's sonnets and instructing her to skim the book as fast as she can. She does — and remembers the entire sonnet sequence perfectly afterwards.