Epiphany

One particular moment sticks out at me as I finish the novel: the moment when, about to be beaten again without cause, Frado commands Mrs. Bellmont to "Stop," saying, "strike me, and I'll never work a mite more for you."  It seemed to me that this would always have been a legitimate threat, as Frado is a free woman, despite her lower class status.  I could understand that this was simply an avenue that she hadn't explored until this point, a thought so emboldened and outside the realm that it took Frado time to conceive of it.  But in my view, this could have been the end of the book (or the end of the story in real life, for that matter).  Wilson writes on the next page, "Thus passed a year.  The usual amount of scolding, but fewer whippings."  Why does Frado endure any whippings at all?  It is clear that Mrs. Bellmont needs her more than she needs Mrs. Bellmont.  She is in a position to resist the whippings, the kind of treatment that characterized her time with the Bellmonts to that point.  This should have been the end of such treatment, and, in essence, the end of the story, but it wasn't.  Frado in fact spends a good deal more time with her tyrant, and we never again see an instance when she herself refuses to be beaten.  Is this simply the result of a damaged psyche?  Or is there some other pragmatic concern that prevents her from acting that I just missed?