Story of the Character
Heather was a frequentist of the Newport Union and disliked Marissa Cooper from the very beginning, harassing her and doing all she could to make the girl life as difficult as possible. She helped Kevin Volchok "kidnap" Marissa, to convince his enemy : Ryan Atwood, to clash against him.
In an episode of the series she got drunk, then some of Volchock's friends took her behind in the van and had turns with her, and they almost rape her. They were stopped by Marissa who then broke up with Volchok. Heather, was in the car when Volchok drives into Ryan's car, leading him to drive off a cliff which results in Cooper's death.
At the end of same season, after the girl death, she and Volchok escape together.
In Season 4 she appears briefly and apologizes to Ryan about the night of Marissa death but claims to have no control over Volchok actions.