When Beatrice thought her father was innocent it would have made sense for her to think that all he had to do was tell the truth. I can see, under that circumstance, her encouraging him to clear his name. In retrospect, he stepped on a rake. The smart move was the old axiom of "never complain, never explain" and let the palace manage the pr and legal matters.
The four Yorks were always very close and I doubt the princesses scrutinized their parents' associates very closely. Right now they're probably in damage control mode for themselves and their families. I can't imagine how disgusted they are with their parents and how foolish they feel.
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