It's one theory proposed by a Hungarian revisionist.  From what I have seen about this case, it is not a very likely one.  There's always someone who comes along and says the most foul, guilty monster in the world was framed.  Still, many people say the "Blood Countess" was unfairly imprisoned by the Hapbsburgs.  She did not get much of a trial at all.  My view is that the stories about her bathing in blood her likely spread to cover up their own complicity and inaction for many years.  As for her real motives, that is still a mystery.