I have seen the film, and didnt quite understand the end either telbell. Which is not much help to your wife, but at least it shows she is not the only one :(
Hi there - not seen the film myself so hope this is the right film ("Cache" in French)
Try this link to imdb - scroll down to the message boards section and someone may have posted a similar question there. You might have to join the site to access the message boards but it's free so ..