I don’t think that there is one character who is the Blue Fairy and the Black Fairy. I hope not at least, but i do think it is possible that it is the Blue Fairy who is the evil character and maybe have been called the Black Fairy in the past and maybe banished the character we now know as the Black Fairy and then told others that she was evil. I like the idea that the Blue Fairy is actually Rumpel’s mother. I think that would be way more interesting then random new character being his mother. Though, i also think it seems consistent that the Blue Fairy would be upset that the Black Fairy was pregnant and with Pan especially after how she reacted to Nova liking Grumpy.
I, definitely, think this title suggests that who the Black Fairy originally was and, therefore, potentially who Rumpel’s mother was will be different then what we know now. AKA, the Blue Fairy is shady.