This is a difficult question to answer because one's ideological and critical perspective must be specified before a determination on Fanny Fern's literary worth can be made. The two dominant critical perspectives are cultural canon and classical canon.
Culturalism advocates, in brief, developing a canon of literary works based on literary voices not previously attended to under the sway of classical canon. These literary voices may include women's voices (e.g., Fanny Fern, Anchoress Julian of Norwich), ethnic voices (e.g., The Color Purple), contemporary voices (e.g., The Outsiders), post-colonial voices (e.g., The Farming of Bones), and cross-cultural voices (e.g., The Lone Ranger).
By this approach to canon, four important criteria are (1) cultural or social revelation or relevance (e.g., Ruth Hall, "The Bear"), (2) silent voices expressing non-mainstream reality (e.g., Things Fall Apart), (3) surprising or socially unacceptable resolution (e.g., "The Awakening"), stories and lives of common, everyday characters and trodden down characters. By these criteria, Fanny Fern's essays and novel, Ruth Hall, would fit a cultural canon and be appropriate for a culturalist college classroom. The question here is: While culturalism may be valid, should it supplant classical canon and be all one reads of English Literature or American Literature or should cultural canon be a required subset of English and American literatures?
Classicalism advocates, in brief, a continuation of the novels that began the study of English literature in the 1800s. These were the great male writers of the previous century--who had the benefit of university education and study of Greek and Latin works--beginning with Defoe. The English pedagogical belief was that literature led to the development of inner character, courage, loyalty, a sense of duty and reasonable thinking. Literature study prior to the 1800s meant exclusively the study of Greek and Latin literature. Classical canon carries these originally studied English novels forward to today and adds whatever titles that are deemed to be equivalent of and equal to or surpassing those early novels.
By this approach to canon, four important criteria are (1) revealing universal realities seen as applicable to all humanity, though "universal" was defined by their unavoidable non-global European isolation; (2) contribution to development of high moral, ethical, mental and inner character traits; (3) excellent mastery of language; (4) Aristotelian description of lives of elevated characters, not common, everyday characters. By these criteria, Fanny Fern's works certainly do not fit a classical canon nor would they be appropriate for a classicalist college classroom.
The book’s also a fascinating mixture of anger and sentimentality. Ruth is as misunderstood and put-upon as any romantic heroine, beset by hypocrites and by fate. Her Cinderella ending is the product, however, of her own talent and determination. (Pat Pflieger, "Ruth Hall, by 'Fanny Fern' (1854)")
The question that emerges is whether the emphases of culturalism are important enough to either complement, through required partnership, classical canon or to wholly supplant classical canon.