What I think happened at the end
He poisoned her. The director gave us a few close-ups of the glass she was drinking from. And after she took a last sip she stared, almost as if she felt it kicking in, with a worry and realisation in her eyes, then the movie finished. Maybe her drink was poisoned and she fell flat on the table straight afterward.
It mighy not be that deep. Edward didn't seem like a killer. Maybe he just wanted her to feel what he felt during the breakdown of their marriage. And after he stood her up at the restuarant, his job was complete.
(But i prefer the poison ending ;)