Given the nature of Pulp Fiction's many intertwined storylines, it could be any of the unsavory characters. It could be Vincent Vega or Jules Winnfield if they were involved in a situation where they had to deal with a woman in a drug - related or dangerous context. Or it could be some minor character who we don't really focus on much but is part of the seedy underbelly of the movie's world. It really depends on the specific scenario within the movie that this phrase pertains to.
Well, in Pulp Fiction, since it has a complex web of characters and situations, it could be any number of people. It might be one of the drug dealers or some low - life criminal who is involved in a deal gone wrong or some sort of power play. Maybe it's a character who is trying to control or harm the 'her' in the statement. Without more details from the specific part of the movie where this phrase is used, it's hard to say exactly who.