Mommooshka SPOILER: I agree. However, the years that passed after her death and until the story took place was certainly not a typical childhood and exposed her to a lot of time and experiences outside the norm. Also, as an only child raised in an all-adult environment where she was treated in many instances as a little adult, she would also be more mature than other kids. I've seem this in real life with many only-children. And like you, I loved this book on many levels, too!
Jayna Her parents were both scientists. She grew up reading her mother's scientific findings. One would expect her to be well above average.