Three teens (Ashanti, Sophia Bush, Arielle Kebbel) discover they’ve been sharing the same boyfriend (Jesse Metcalfe) and conspire to make him fall for a reclusive pal (Brittany Snow) who’s bound to break his heart. Betty Thomas, directing a script by TV veteran Jeff Lowell, seems uncertain whether to sympathize with her three heroines or with the title cad, but there’s something mildly charming about this cheerful revenge comedy’s lack of any straightforward moral agenda. PG-13, 87 min. (JR)