my crack theory–she is the wicked witch but in the cursed identity she thought she was Miss Deville fashion designer and she wants revenge on Regina. So she has her memories in this next curse in the same way rumple built in a fail safe for his.
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“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass