Truth of horrid choices

WARNING: depressed thoughts are in this book. It may turn suicidal but I know will go away, meaning that the thoughts will go away and she will be somewhat happy. (12+ recommended age)
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No one needs to know, that is all Kai Goodman thinks in her mind everywhere she goes. She goes through depression and is left as an orphan to this day at the age of 16. Her friend Luna Mann comes into play and tries to help all that she had left of her good friends' sanity. Slowly breaking, Kai reveals a secret that changed her and Luna's friendship for a good while. Someone else comes into play and is later found out to be someone close to Kai and has the exact same ordeal that Kai and Luna have. Soon to be found out are truths that were turned into bad lies in the beginning..