When Grace is given the breakfast order at the beginning of the film the eggs on the plate are crispy and burnt. Yet when she hands the food to the customer the eggs are clearly different from the ones on the plate before.
The airport stamps in passports of Meg, Grace and Emma are dated June 19, 2010. The stamp in Owen's passport is from June 22, 2010. However, when Owen arrives to Monte Carlo, he shows the issue of the newspapers from June 10, 2010 featuring Emma, Grace and Meg on the front page.
When Meg and Emma meet while out with their respective dates, the Aston is on the right and the scooter on the left. A moment later, when Riley acknowledges the prince, the Aston is on the left and the scooter on the right.
Emma is watching Grace Kelly in To Catch a Thief in the hotel room in Monte Carlo. When Grace Kelly became the Princess Consort of Monaco all of her films were banned from ever being shown in the country of Monaco, including the capital city Monte Carlo.