>>716060074
Well, that depends on your definition of good witch. If it's all about casting evil curses and the like, I don't doubt she'd be capable but she wouldn't be particularly good because her heart wouldn't be in it.
But if it involves the study and practice of dark magic, then absolutely. She's a pretty competent spellcaster already and her bookish nature would be of much help.
In fact, she can reclass to witch in her game, gaining access to dark magic and some pretty unique skills like warping and alchemy. I haven't played with it personally but I've heard she's exceptionally good in that class.