The little English woman, as she was affectionately called by friends, was actually of Irish descent, daughter of mathematicians, composer and novelist including The Gadfly. Born in Ireland in 1864, raised in London, studied in London and Paris, taught music in St Petersburg and Irkutsk, married in London and moved to New York where she remained until her death in 1960.
One of the main characters of this novel and author of perhaps the most published young adult novel ever.
More information about her can be found on Wikipedia.