Heartbreaker (2010) on Netflix

Plot summary

Alex runs a small agency with his sister Mélanie and with Marc, her husband. Clients are relatives and friends who want a woman out of a relationship she is unhappy in without knowing it, and the agency stages elaborate tricks to that end. A wealthy florist with links to crime disapproves of his daughter Juliette's engagement to Jonathan, an English millionaire, and wants the wedding stopped. Mélanie and Marc study the pair and find nothing they can use. Alex refuses the job at first, but debts to a loan shark and heavy spending on the agency force him to take it. Juliette travels to Monte Carlo ahead of the wedding, and Alex arrives there as her bodyguard.