This female buddy flick with elements of chaste rom-com and coming-of-age conventions teeters to the edge of decent escapist entertainment but doesn’t quite make it over. Teen queen Selena Gomez stars as Grace, a recent high school grad from Texas who’s been saving the money from her waitressing job for a trip to Paris with an older colleague (Katie Cassidy). After Grace’s sourpuss stepsister (Leighton Meester) is added as last-minute baggage, the trio set off for France, only to take a detour to Monte Carlo when Grace is mistaken for a posh celebrity. Each of the girls gets some sexless romance, Grace’s impersonation results in sundry hijinks and the French are ridiculed for being French. For all its perfunctory efficiency, Monte Carlo is an airless balloon of a movie, lacking in energy and heart.