Another idea.
Blackmail.
If it's good enough for them, its good enough for us.
Tell her you will go to the JC if she gives you a list of years of the Babylonian kings from Nebuchanezzar to Nabonidus, showing which king reigned in which year, quoting her sources.... and.... it has to back up WT chronology. No excuses. No changing the subject. No re-phrasing the question.
Everything has to be honest and above board and if she can't do it she has to tell her husband to call the dogs off until he has a king list to give her to give to you.
The longer you leave it before you confront your parents with the reality of their poor choices, the harder it is for them to admit their mistakes.
Mine had been 'in' for 65 years before they had to confront the implications of their poor choices. I feel sorry for them but....... It was their choice ... I have to live with my choices just like everybody else on the planet, why shouldn't they??
((((Bottle))))