Queen Mab #Film: "Mab appeared as the main antagonist in the 1998 fantasy mini-series, Merlin. She is portrayed as a cruel, power-hungry, somewhat sociopathic goddess and the twin sister of the Lady of the Lake. She is mentioned in the movie Fairy Tale as the fairy queen."
Unless they didn't just borrow the name for no particular reason, the character has the potential to be interesting, (especially if they'd consider a connection to the Lady of the Lake in any way).