The Hank/Donna change destroys her character?
When you re-watch the film, Donna's character is borderline evil.
We see Hank (Donna), Arctor's supervisor continuously lie and push Arctor into insanity.
In the book, she isn't Hank so her actions are reasonable. When you combine the two characters (as the film does), some of the dialogue is brutal.
e.g. Telling off Arctor for taking D, saying that no-one pushed him into it.
It makes the 'remorse' she shows completely illogical since she is completely responsible (as Hank and Donna) for every development on the job.
It would be like pushing people into a gas-chamber every day for a year, and when it's over, suddenly wondering whether you went a little too far.