Yeah, I think it’s very possible that Cora is the Queen of Hearts. My guess would be that she went through the mirror in to Wonderland, went about gaining power to become the Queen, and then when the curse struck the world’s merged and she ended up in current fairy tale land. I only have one issue here, and that’s the time difference. Regina’s wedding was many, many years ago. So how come Cora looks the same age as she did then? I suppose it’s possible that she went directly from the mirror to present-day. Or maybe you don’t age in Wonderland?