This is me as well, I remember I read this book called, "Skinny" about a young woman with anorexia who wanted to become a doctor but her mental state declined further and further away from her goal. Which also destroyed the people around her, and her sister had a slight learning disability and a hearing aid but she loved sports and was extremely good at it. The two sisters were the main characters, and not to be rambling on too much, 'Holly' (Sports Sister) slowly watches her older sister Giselle (Doctor Sister) die in front of her eyes over the course of the story. In the end Giselle dies and some people believe that Holly, losing both her Father (which is also a huge piece of the plot in the novel) and her older Sister, commits suicide at the funeral. The ending haunted me for dayyysss and had me tearing up on a few occasions. So I definitely know what you mean!