One Small Hitch (2013) on Netflix

Plot summary

Josh Shiffman and Molly Mahoney have known each other since childhood. Both are flying from Los Angeles to Chicago for the wedding of Molly's mother. Molly is bringing her boyfriend, but she has told her family nothing about him, not even his name, since he plays in a band. Before they reach the airport she learns that her boyfriend already has a wife, and they part ways. At the airport Josh's parents call him, and he learns that his father, Max, has cancer and is expected to die within six months. Max says his one regret is that he will never meet the woman his son marries. In a moment of panic, Josh tells his father that woman is Molly. She agrees to act as his fiancée for the weekend.