yeah, thats sad story, that she lived so long, and forgot almost everything, because filolials not have that big memory capacity... well, they are still birds
@Ammaple27 they lived in ruins, and in main story there was nothing like memo/note/paint or something she made to remember. just that she remember just her promise/mission and forgot all else.
@CronosusCZ: Even human's would forget about thing if its hundreds of years old (assuming one is alive for that long, and still sane).
This is the hard life of those who live a long (fulfilling) life, and the ones close to them die earlier than them.
@Kidawesome55: In the WN, yeah it was stated (it is a big spoiler relating to the climax of the WN story).
But not sure if the same plot would be used in the LN and later in the Manga or not (as the Author is changing the story somewhat between the WN and LN).