Heather is a frequentist of the Newport Union and disliked Marissa Cooper from the very beginning, harassing her and doing all she con to make Marissa's life as difficult as possible. She helps Kevin Volchok to kidnap Marissa in order to get Ryan Atwood to fight Volchok. When she had gotten drunk some of Volchock's friends took her behind in the van and had turns with her. They were stopped by Marissa who then broke up with Volochok. In the third season finale, she helps Volchok to leave Newport in a stolen car. She is in the car when Volchok drives into Ryan's car, leading Ryan to drive off a cliff which results in Marissa's death.
In Season 4 she appears briefly and apologizes to Ryan about the night of Marissa death but claims to have no control over Volchok's actions.