The thing is, unlike novels and that weird webcomic your cousin publishes on DeviantArt, screenplays are rarely written by a single person. While only one or two people may get credit for it in the film's final list of credits, uncredited (but well-paid) script doctors are routinely brought in to punch up dialogue, resolve plot holes, and sometimes rewrite entire swaths of the story. It's sort of like when your less-literate friends ask you to help them with their cover letters.
Fisher was one of Hollywood's top script doctors for 15 years. Some of her more famous movies include the aforementioned Hook, Sister Act, Last Action Hero, The Wedding Singer, Coyote Ugly and Scream 3. And yet, not even she could save the inexplicable dialogue that came spilling out of people's heads in the Star Wars prequels.
"I don't like this dialogue. It's course and rough and irritating, and it gets everywhere."
Unfortunately, she's since given up the work, saying that times have changed and studios are wanting people like her to do punch-ups for free, because they apparently feel that Fisher needs to build up her resume. Instead she's banking on reprising a role from a science fiction trilogy she starred in back in the '70s and '80s.