@adfjs With a decent learning tool, like a flashcard app, hiragana and katakana aren't that bad. I memorized those in a few hours back in college, and only needed the occasional refresher to remember them for 6 semesters of Japanese.
As for the kanji, it looked like she was looking up the meaning for a few of them, so he probably just meant that she had already moved onto learning some basic kanji and words.
He does describe her as a genius at some point, so she probably is abnormal, but memorizing under 100 simple characters in 2 hours isn't impossible.