Board Thread:Spoilers!/@comment-6175354-20131205143032/@comment-5655661-20131205232401

Bold guess - original Sleeping Beauty aka Aurora's mother. This show really likes familly issues so I won't be surprised if this new character is someone's mother, aunt or something. That's just my guess, but more likely, it's either Cruella (which I hope she's not) or the Evil Witch from Rapunzel story.