The things that made it into official accounts were bad enough that if she hadn't met the man, she would've thought him irredeemable, too. In spite of what Luke thought; Luke hadn't been the best judge of character when she'd met him. But she isn't here to argue Vader back to the Light.

"As far as I can tell, you're the only one who refuses to see good within yourself."

It's irritating, really -- she'd have found it much less complicated if he were entirely lost to the Dark. As it stands there's still a part of her that feels like she's betraying herself and everything she stands for by having this conversation. But given what he'd said about Obi-Wan, maybe not. Maybe she was doomed to care even for those who were beyond saving.