The whole story is like Luke turning to the dark side instead of saying “I’ll never join you”. Holocaust deniers usually deny it because they’d like to do it themselves.
Technically, what you’re proposing regarding her is more like Luke deciding to kill Vader despite knowing he’s his father and heeding Obi-Wan’s statement of killing him, and THEN turning to the dark side anyways. Remember, speaking out against your father =/= being a good guy. In fact, Citizen Louis voted against his own brother for the death penalty, and I don’t think many people would call HIM good.