The Nancy Estabrooks you refer to is mentionned in "The Genealogy of the Anglo-Dutch Estabrooks Family" (1935) by Florence Estabrooks. On page 78 she is listed as (151) Nancy married a Mr Keene. Children listed are Thomas Edward, Amanda, Harriet, Judith, Victoria, Nancy, Ann, Berrtina, Albion and William.
Nancy was daughter of David and Judith (Fletcher) Estabrooks of Wakefield, Carleton county, NB and Calais,Maine, both of whom were alive in 1870 in Calais. Nancy's father, David was born 1791 to Ebenezer and Maria (Fletcher) Estabrooks. While I am not related to this Estabrooks family, I am in possession of a copy of the above mentionned book, using it frequently to do look-ups. I have not seen any reference to Metis or any other native ancestry within this family.