Happy Birthday streaming

A family gets together one summer day to celebrate the mother's 70 birthday. There's her husband, their two sons, one with his wife and their two boys, the other with his new girlfriend, a movie camera to immortalize the event and a young woman eighteen years old who seems to have grown up here. Things seem peaceful and joyous until the unexpected arrival of the younger sister who had vanished four years before. She is greeted like the prodigal daughter but brings chaos in tow.