Complex sentence: The epistolary section represents the third style, which was a newly developed trend, one that Bowring considers the weakest portion of the work, because he believes in that section she fails to break free of the rhythms of spoken language.
Split into simpler sentences: The epistolary section represents the third style, a newly developed trend. Bowring sees this as the weakest portion of the work, a section where she fails to break free of the rhythms of spoken language.