Factual error: In the deleted scene where Bill kills the black guy and his henchmen, Bill slits the throat of the black man, and then sheathes the sword immediately. This would cause the blood to clot the inside of the scabbard, making it sticky and difficult to draw the sword. And if left long enough, it would rust the blade. The scabbard will have to be taken apart to be cleaned properly, which would be a lot of meaningless extra work, instead of simply taking 5 seconds to wipe the blade. A swordsman of Bill's caliber would never have mistreated his weapon like that. It is like seeing a soldier deliberately burying his rifle in mud to give himself a nice, long job of cleaning afterwards.
Factual error: When Beatrice arrives in Acuna, Mexico, she drives through a jungle of palm trees. While jungles exist in southern Mexico, Acuna is located on the Texas border and the landscape there is flat sagebrush desert.
Chosen answer: The way she talks to Budd as he lies dying, seems to indicate that she has disliked and hated him for years, plus the fact that she feels that he was not "worthy" of killing Kiddo (seeing how Kiddo was a fantastic warrior, while Budd is an alcoholic hick). However, it would be difficult for her to get close enough to kill him earlier, as he would not buy any excuse why she just came visiting. But when Budd actually invites her over, she gets a chance to get back at him, and in the same while take the credit for killing the Bride and retrieving her Hanzo sword for Bill. Vengeance and personal gain in one swoop.
Twotall