So long Mischa Barton and Sebastian Knapp. The O.C. star and her actor boyfriend have broken up. A source tells US Weekly that the pair, who was first linked back in 2012, actually called it quits a few months ago. However, it didn't appear Mischa was in post break-up depression just a few days ago at a red carpet event. The actress looked happy and gorgeous as she struck a pose! So, what about that O.C. reunion? You're going to have to watch to find out!