The formerly unknown dispute is about the book's depiction of the harsh conditions at the Lowood School, which Bronte based upon her experiences as a student at the Clergy Daughters' School in Cowan Bridge, Lancashire.
She used the school's founder, Rev. William Carus-Wilson, as the inspiration for Mr. Brocklehurst, Lowood's headmaster.
The letters suggest that Carus-Wilson didn't like the portrayal of the school and himself in the book and sought legal advice. To avoid legal action, Bronte wrote an apology admitting she had exaggerated the details, The Telegraph reported.
The author's apology letter has not been found, but three letters by Carus-Wilson's grandson, written in 1912, have disclosed the dispute. The grandson apparently sold the Bronte manuscript in that year to pay his child's medical expenses.
The Carus-Wilson letters have been put up for auction and are scheduled to be sold on June 21. They are expected to bring around $200.