The End
Imagine you sent your ex a novel you wrote after she told you you'd never amount to much, that you were merely a dreamer, and that you wrote too much from your own experience.
And this novel is a gritty Western genre piece that serves as a metaphor, with themes and characters blended so that a direct correspondence between these aspects, and the experiences and people they're supposed to represent in real life, is somewhat difficult--but one that nevertheless registers on an emotional level with your ex.
Now imagine your ex is dissatisfied with the life she left you for--the same life that she chose which placed you in the turmoil that was the genesis of your novel. And...now she wants to have dinner with you after she's finished reading it.
Your ex sends you an email. She apparently hasn't understood that after all that she's done to you, after all the rage and pain, leaving you like the broken protagonist who dies in the novel you wrote, that you wouldn't be open to meeting with her. Your ex doesn't get that you sent her your manuscript because you wanted her to understand what she put you through--that sending her your manuscript was your message. Not only that, but your ex thinks that she can just leave the life which she left YOU for and that you two can start again.
For most of us, we'd just never respond to the email.
But THAT would be a real non-ending--because, after all, this is a movie.
So that's why Edward agrees to a meeting, and we see Susan getting dolled up, leaving her wedding ring, only to get stood up at the end.
It's not a non-ending. There's just really nothing more to say, Susan.