The plot: Jane (Katherine Heigl) is always a bridesmaid never a bride. She's in love with her boss, George (Edward Burns), but her sister Tess (Malin Ackerman) is the one who actually ends up with him. Only problem? Tess isn't who George thinks she is.
Crappy message: Jane is mad that Tess is with the guy she wants to be with, so she sabotages the couple's wedding and reveals all the ways that Tess has lied about herself to George. Sabotaging weddings -- even your sister's! -- is a totally reasonable response to not getting your way.