Looking across the history of reactions to The Female Quixote I believe that nobody has ever seemed happy with the ending, not even the ones who agree that Arabella needed to be reformed. It happened so quickly that the (this is my paraphrase:) realism of reasonable pacing was violated.
It switches to Rasselas shortwindedness in which an abstract represented by Sir Charles seems not only pre-assured but imminent. Arabella’s Romantic mental fantasyland is dispelled through logical argument; and quickly, quickly she has expressed humility and married Mr Glanville.
The author, taking a new self from herself, moves at a fantasy speed, as if she wishes she had the dream-instantness that happens in Powys’ novellas, but as a proponent of realism she has removed her own access to that usefulness -- she has been aligning herself with the opposition for over three hundred pages now (in the Oxford University Press, 1970 edition), though at this point in the historical development of the book she can still write a variation on then they lived happily ever after – I mean she has this shorthand for happiness still available to her.
Mr. Glanville and Arabella were united, as well in these [titles and finances], as in every Virtue and laudable Affection of the Mind.
In book IX, ch. 1, before her conversion, she walks into a crowd of sailors in Vauxhall who are teasing a woman who has come here dressed as a man – come with me, says Arabella: you are clearly a noblewoman whose current adventure has caused her to wear a disguise. And the woman is so amazed by this statement that she behaves as if Arabella’s belief is true. “The Girl being perfectly recover'd from her Intoxication by the fright she had been in, gaz'd upon Arabella with a Look of extreme Surprize: Yet being mov'd to respect by the Dignity of her Appearance, and, strange as her Words seem'd to be, by the obliging Purport of them, and the affecting Earnestness with which they were deliver'd, she rose from her Seat and thank'd her, with an Accent full of Regard and Submission.” A moment later Mr Glanville is pulling Arabella away and telling her not to “make all this Rout about a Prostitute. Do you see how every body stares at you? What will they think --”
I have a fantasy in which the woman goes home with Arabella and actually transforms herself into the thing that she believes as easily as someone in Powys, or Max Jacob, or becomes something else magically instead. (“At this point, Sir Elizabeth joined the military and was killed.” Jacob, tr. William Kulik.)