case of "internal persuasion". Doesn't it sound like some malign affliction of the mind.

I am of course thinking of Fanny Dashworth and her supremely intrepid way of reasoning, so that in the end her husband's sisters and mother need little more than a roof and a loaf of bread a weak to live in perfect comfort according to her.
Selfishness is guiding these two women and there is never the smallest glimpse of sincere compassion or care for other human beings.
Charles may congratulate himself that even though he lost the best Elliot sister, he is not landed with the worst. Childish Mary is by far to be preferred to chilly Elizabeth.