Over Her Dead Body

Devastated when his fiancée Kate (Eva Longoria Parker) is killed on their wedding day, Henry (Paul Rudd) reluctantly agrees to consult a psychic named Ashley (Lake Bell) at the urging of his sister Chloe (Lindsay Sloane). Despite his skepticism over her psychic abilities, Henry finds himself falling hard for Ashley, and vice versa. But there is a big snag. Ashley is being haunted by Kate’s ghost, who considers it her heavenly duty to break up Henry and Ashley's fledgling romance, if it is the last thing she does on this earthly plane... (Source)

A woman discovers her new boyfriend is being haunted by the annoyed ghost of his former fiancee. (Source)