...because she never got that far in her thinking. The prospect of shaming herself in front of him was enough to put a veto on her going to Pemberley until she was sure he was not there.

Had there been no shame in going, would she have thought about paining Darcy? Probably. Lizzy was in general a compassionate person, even when she was trying archly to vex someone. But in this case, I do not believe Lizzy's thinking ever got that far; the personal shame of being found there was daunting enough to stop all consideration of the matter.