First of all I have to say that it is worth seeing...an inoffensive, cute, funny and predictable romantic movie.
Reese Witherspoon makes the movie, of course, as an over worked and driven intern in a local hospital who has no time for romance. Why that is, we never really find out, or maybe I was just too inattentive to catch it, but her avoidance of personal relationships is key to the movie.
Without giving away the plot device I will say that she, her spirit, haunts her former apartment, which has been rented to another pained soul, Mark Ruffalo. Mark is still brooding about his own romantic tragedy, and his interaction with the spirit of the not quite dead yet Witherspoon is what the movie is about.
Mary will probably like it and it may touch a sentimental chord in you as well.
Go ahead, rent it!