Something not yet considered (at least here). BF is stated as being the original power, which is may be more legend than fact. This would seems to imply she is the original power for good and evil magic, what if she removed the evil magic into another entity – the Dark One. Such a entity that could be more easily controlled by greed and ambition of the Dark One and other humans keeping such a power in-check with perhaps some Fairy assistance.
Someone brought up that it seems strange for the Dark One’s magic to just disappear without going somewhere…. what if the result of a true love kiss is the Dark power returning to BF, which could potentially have dire results. In this situation, getting rid of Dark One by sending it to a magicless world, effectively imprisoning it, was the only way to rid FTL from the Dark One’s magic.