Create a file called whatever.rpy in the game's 'game' folder, paste this inside...
Code:
init python:
config.developer = True
...to enable the use of console commands.
Now start the game, load your save (or start a new game and get past the photo showing thing), press Shift+O, paste this...
Code:
f = Character("[f1]", image="fairy", who_outlines=[(2, "#fff")], who_color="#24a80f")
...press enter, then escape, and the fairy has a proper name once more.
It seems some file handling code is overwriting the variable 'f' which is used for the fairy character. Only affects a new game though, not loaded saves.