V.C. Andrews 
April Shadows [EPUB ebook] 

April had always felt like an outsider…Her older sister Brenda was tall, athletic, competitive, and sure of herself. But April Taylor was short, sensitive, and overweightand she couldn’t bounce back from their father’s cutting criticisms the way Brenda did. April didn’t know why their once-loving dad had become a coldhearted monster, but she was sure it had something to do with her. And she could see how his cruel behavior was tearing away at her gentle mother. But a glimmer of happiness returns when Brenda brings home her college roommate: beautiful, bewitching Celia. And April wonders if she might not be so different from Brenda after all…