The main character was a young girl with an older brother named Jack- Jack becomes sick and is soon diagnosed with cancer or some other life threatening illness (my memory is foggy). At the hospital where Jack is being kept, the main character meets another young cancer patient named Lara, who gets in trouble from her mother constantly for smoking, despite her illness. The main character has a love for horses, I believe. I don’t remember exactly, but I think there might have been a chapter where her and her friend from school go horse back riding. The book ends with Lara dying, but that’s all I remember.
Lost Classics of Teen Lit: Name That Book! 