On WikiTree we currently have Nicholas II's maternal line ancestry back to Kathryn von Pfannberg but her profile is unsourced as are several descendants.
I think I've seen something that states that Barbara von Cilli is the maternal line ancestor for which every generation from her to Nicholas II is definitely confirmed. Any maternal line ancestors of Barbara von Cilli are possibly unsure or disputed?
I'm not sure where Eupedia gets the information to take the line back to Adelheid von Alpeck? Whether it comes from reliable sources or just what might have been found online?