How has Melinda's ex best friend Rachel changed in high school

Rachel is Melinda’s former best friend. Rachel hates Melinda after Melinda calls the police at a summer party to which Rachel’s brother had brought them. Rachel begins spending time with the foreign exchange students and changes her looks, her attitude, and her name to Rachelle. In the spring, she starts dating Andy Evans, and Melinda tries to warn her of the danger of being with him.