Bottrall, Margaret, ed. G.M. Hopkins, Poems, A Casebook. Macmillan, London, 1975.
Hartman, Geoffrey. Hopkins: A Collection of Critical Essays. Prentice Hall, Englewood Cliffs, N.J., 1966.
Mackenzie, Norman H. A Reader’s Guide to Gerard Manley Hopkins. Thames and Hudson, London, 1981.
Thornton, R.K.R. Gerard Manley Hopkins: The Poems. Edward Arnold, London, 1973.
is she someone important in his life, could someone please give me some info about this topic???
A bit late to be answering the previous comment, but no, Hopkins said the poem was "not based on a real incident".
By the way, although I'm sure Hopkins would have been happy to use an Americanism, "fall" was used as a term for the season alongside "autumn" from the 17th century in Britain, although by the 19th it had rather gone out of use (unfortunately -- I am English, but I much prefer "fall" to "autumn"), so its use in the poem could be either American or slightly archaic.