Mary-Kate Olsen and Max Snow have called it quits, her rep exclusively tells In Touch.

The couple started dating last September and got very serious very quickly. But Max, a New York based rocker, and Mary-Kate, both 21, split due to her busy career. “They broke up mainly because she was in LA and Max was in New York, which made the long-distance relationship tough,� says an insider. Since the breakup, the multimillionaire former child star is putting her career first. “Mary-Kate has been busy filming and working with her sister, Ashley, on their new fashion line, The Row, along with launching a new clothing line called Elizabeth and James,� says the insider. In addition to her role as Tara Lindman on the Showtime hit Weeds, Mary-Kate has been filming The Wackness, in which she shares a kiss with Ben Kingsley. Max’s cousin is actress Uma Thurman and his brother is artist Dash Snow. Mary-Kate has been out partying with her girlfriends since she split with Max.