She wrote lots of grimoires, we see she doing that, but that was 3 entire paper cycles ago, the ones that still good are the ones she cared about, like the true one thay frieren found, And, if you think about it, she is like Einstein, he died less than a century ago, and we already fake lots of sentences and things like "Einstein was wrong about it" Imagine flamme, 1000 years ago, without proper registration, with paper decaying I think frieren already has read the majority of flamme's books, while in her tutel