@RobZilla:
Well she was described as the "undefeated woman", rather than the "undefeatable woman", there's quite a difference between those two.
Also, there's different types of strong fighter. Rebecca's reflexes have been shown to be rather incredible (possibly due to some latent usage of CoO) and so far is the only person to have dodged an attack from the ultra fast Hakuba.
You're right, I missed out on that on. Still, I know that Oda puts alot of thought into his work, that's why I admire One Piece so much. But somewhere in his thought process, he came up with "I'm gonna introduce a character called "undefeated woman". She'll constantly lose and cry. Her biggest strength is dodging and she actually hates fights." Nothing wrong with having a character like that! Not every character can be tough and a war-machine. But giving this character the title "undefeated" kinda gives me an impression of "this is my definition of how an undefeated woman is like". And it's not a flattering definition.
That's correct, but in a Shonen Manga, where there is no such thing as "ring out", fast reflexes won't win a fight. If you can't scratch your enemy, you'll have a hard time winning… you may count on wearing them out, but I doubt the audience would approve of such a character. She may be battle-ready in a way, but when it comes down to actually "throwing a punch", the essence of shonen, Rebecca can't do much - if anythign at all.