Come to think of...
Could it be that Sade fell for Alice's father instead of Victor?
I mean she told in past that 'that' person died, but Victor was still alive back then, right? Unless she had total awareness about the future
She did not acknowledge the Duke when she saw him. Her attention was fixated on Alice - Sharon's daughter.
Another titbit - it may be possible she straight suicided later through those sorcerers in her crazy style ('I can take on a hundred men or two, duh'). Still, she made sure to mess with Sharon even beyond the grave. Now that's a grudging.
Also, being forced to hear thoughts 24/7 can really screw up one's mind. It could be she really saw what she had done to Daleth as some form of 'tough love'.