Help Name That Book.

I'm looking for a book where a woman conceived a child a few days before she was raped and everybody, her included, thought the child was a product of it. She kept the child, a daughter but the whole family, the mother included was mean to her. The girl's siblings got huge birthday parties and gifts, she didn't. Everybody in the family, except for her, had a study fund. the only who cared about her, was her godfather. Her siblings got cars on their eighteenth birthday and she was hoping to get one to. When she went home after school, I think, on her birthday, her parents were waiting outside for her with all her stuff packed and told her that they did their duty and that she is now on her own. They found out years later, when she was in her twenties, when her father became ill, that she was his biological daughter.