[Antera Caramichael]

Spoiler for Clarification of the Three characters:

Well, it is like this:
Rika is the first original character. When Lambda engaged a game (But against who?), Rika was the only character to remember most of the previous worlds. With Umineko, i think we can say that Bernkastel was the Battler of Higurashi: The first original Rika, Meta-Rika in brief =p. After defeating Lambda, she was called "Witch of Miracle" because she succed to defeat "the Certainty (Lambda)".
I think the Rika in the game, Piece-Rika in brief, remembered the previous games because Bern gave her her memories from the previous game in order to go forward. OR maybe it is a natural phenomene as the main piece of the game (Could we see Battler remembering previous games?).

Furudo Erika is Bernkastel piece, and if you look at her behavior, she is totaly different from Furude Rika who is in both her personnalities not sadistic at all... if you look how she is humiliating Natsuhi, she is more resembling to Bernkastel, who is no more shocked by anything because of Higurashi's games and is only trying to win at any cost while enjoying it.