Mischa Barton isn’t completely recovered from the wisdom-tooth misery that supposedly landed her in the loony bin last month. A source on the set of her CW show, “The Beautiful Life,” says Barton shows up to work so bleary some days that it holds up filming. One day, says a source, “she was getting snippy with the director and kept demanding that someone make instant coffee for her. Often, she’ll stare at the coffee for minutes at a time and say, ‘Who will fix my coffee? I need someone to fix my coffee.’ ” A rep for Barton had no comment.