That's awesome. She must really have knack for language acquisition then. I feel that, while not impossible, learning a language solely through a medium like anime or television is really (and needlessly) difficult though. At the very least, I'd encourage anyone considering to do so to study grammar and vocabulary through other means as well, since that would only speed up the process.
That is to say, when you have a grasp of different grammar structures, picking out words and figuring out their classification (verb, noun, particle, etc.) is much, much easier, so it's in every student's best interest to do so.
I guess I just don't want someone to hear of your friend's success story and then follow in the same steps without making use of any of the great resources to speed up and ease the learning process.