I'm looking for a book I once read, but all I can remember is a description. Read and see if you recognize?

Okay, so I remember that the girl's name was Cathy and she had been pushed off a balcony while at a small party. Her parents were distant socialites and she was extremely close with her diabetic brother. She spends some time following the case of who murdered her, some time reconnecting with an old friend who we later find out commited suicide by driving his motorcycle into an on-coming truck due to his despair at being injured and unable to play baseball for the rest of his life, and running away from this dark shadow, scary thing. In later books (but I think this was like all grouped together or something) She comes back in a different body, as does boyfriend (The boy mentioned above), and she writes stories that help people until a movie deal that ends in sharks and the oh-so-cliche' of a bad dude making Cathy dig her own grave for telling of a past world-alien-human batlle by accident. She dies - again - at the end. Weird how I can remember all of this but not the title, right? Anyway, just think about it and see if you can help me out any. Thanks.