That was my first thought too.

At the beginning of this new arc, though, I remember you saying that you had first translated "pearl" with "butterfly". Are these two words similarly written in Japanese? Because I think you could have been not totally wrong; Yuuko was certainly a "crimson butterfly", and now Watanuki has taken her place.

Add to that the fact that the mysterious girl made a promise to the Spider Lady, and the whole situation suddenly looks like a trap, I'd say.