Something interesting to consider... the film is already a form of fanfiction. Any element in the movie that wasn't in the short story (the lives of the women, any added details, details that were removed, etc.) were written by other writers and were made up by other artists.
If she felt so strongly about the manipulation of her story, I wonder why she consented to having the film made to begin with? If this was really a matter of principle, she should have put a stop to the films of both BBM and The Shipping News. Did she want the publicity? Did she want money?
I think it's singularly boring of her to try to all of a sudden assert some kind of definitive meaning on BBM in these bitter interviews. It diminishes the story for her to even try to do that. The open spaces idea is so elegent... and just because some fanfic writers go over-board with it doesn't mean that the original concept should be diminished. Also, as many of us know there are lots of fanfic stories that deal with issues contained within the original BBM wiith a subtlty and nuance that Annie clearly wouldn't expect.
These cranky interviews by Annie make me really angry at her, and they go a long way towards a strong urge of mine not to read any more of her writing.
Also, now having read a lot of Larry McMurtry's writing with a comparison to BBM in mind... it's amazing to me just how strong McMurtry's voice is in the screenplay. He was not a passive participant in writing the film.