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IMO this was a young woman who felt trapped by her childhood (the note to the friend which I believe was NOT a tactic, but a cry for help - at a time when she actually could have been helped), a young woman who felt backed into a corner with no way out, a young woman with a past history of physical, mental and sexual abuse, a young woman with a history of drugs, theft and other crimes. The mental illness is there, and IMO it is nurture rather than nature (meaning her issues were caused by many contributing factors).
Therefore, she wanted to be caught. And I'll bet she's hoping the WHOLE truth will come out. About the Tracy 60, about her own abuse, and about any other direct knowledge she has. (None of the above was written to excuse her actions.)