Question: If Bill is behind the death O-Ren's parents, did she know? If so why didn't she go after Bill?
Answer:There is nothing in the film that states or even particularly indicates that Bill is somehow behind the deaths of O-Ren's parents. The only explanation we get is that their death was ordered by Yakuza boss Matsumoto, who brought in the thugs that killed her father. There is a semi-popular fan-theory that the man in white (Pretty Riki) is actually a young Bill, but to my knowledge, this was never confirmed by Quentin Tarantino. (In fact, according to the Kill Bill wiki, Tarantino actually denied they were the same person, but I can't find the source for that.) So there's literally no reason for her to go after Bill. As far as she (and the audience) knows, he was uninvolved in their deaths.
Answer: There is nothing in the film that states or even particularly indicates that Bill is somehow behind the deaths of O-Ren's parents. The only explanation we get is that their death was ordered by Yakuza boss Matsumoto, who brought in the thugs that killed her father. There is a semi-popular fan-theory that the man in white (Pretty Riki) is actually a young Bill, but to my knowledge, this was never confirmed by Quentin Tarantino. (In fact, according to the Kill Bill wiki, Tarantino actually denied they were the same person, but I can't find the source for that.) So there's literally no reason for her to go after Bill. As far as she (and the audience) knows, he was uninvolved in their deaths.
TedStixon
Now that the full version of the film has been released, everything you said has been confirmed. Pretty Riki is not Bill.
jshy7979