Hello westonbirt,

My DD is 17 too. And she also has a history of cutting and self harm, but doesn't like drinking or drugs. What you have described about her behavior sounds like something Valerie Porr describes as "apparent competence." I have pasted an excerpt from her book below.
“For families, this apparent competence is one of the most frustrating, perplexing, and confusing aspects of BPD.”
Excerpt From: Valerie Porr, M.A. “Overcoming Borderline Personality Disorder: A Family Guide for Healing and Change.” Oxford University Press. iBooks.
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Check out this book on the iBooks Store:
https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewBook?id=774941262Your DD17 sounds like she has been fairly high-functioning for a while, so this discovery of evidence that she is still suffering must be so heartbreaking! I agree with Lever and SeaSprite that you need to find a gentle, safe way to help her open up asap. My DD is not an overachiever, but I was as a teen. The "apparent competence" Porr talks about describes my own behavior back then, so I have a couple of hunches about your DD.
Your DD sounds like an overachiever to me and she probably cannot sustain the pace she has been living. Good grades, high level sports, AND a job sounds like a lot of stress for any kid, but for someone with BPD, it is probably too much. I was an overachiever in HS too, but I could not keep up the pace I set for myself. Thankfully, I don't have BPD, but I have dealt with depression since my adolescence. When my stress level became unmanageable, I became depressed, withdrew and shut down. Your DD uses different strategies, like sarcasm and cutting. But I believe she has a very painful, private internal world and I have a hunch she feels a lot of shame whenever she fails in her mind.
I don't know what your DD is telling herself, but my self talk was very damaging back then. I hated myself for not being able to keep up the ridiculously high standards I had set for myself. I had my self-esteem all intertwined with my achievements. I remember thinking no one could possibly love me unless I got straight A's, became a doctor, a great artist, a concert pianist, AND I had to eat a perfect, healthy diet with NO sugar or refined products. My all-or-nothing thinking at the time made me think if I so much as ate a cookie, or got a B on a test, I was a complete and utter failure. It was a recipe for a downward spiral of shame and depression. I wound up taking the proficiency exam and getting my GED because I could no longer cope with high school. My college years were pretty rocky too. I eventually graduated with a B.A. but not until I was 30.
Has your DD been in any kind of therapy since her hospitalization 2 years ago? If you can find a DBT therapist, that could help, if your DD is open to going. The problem with 17-year-olds is they already know everything. (I remember thinking I had enough life experience and that I knew all the answers to help myself.

)
If you haven't already read it, I strongly recommend Porr's book I gave you the info for above.
I don't have any answers, but if my hunch about your DD's high achievement and perfectionism is correct, then I suspect she is hiding a lot of personal shame. Hopefully that will help give you some insight into her behavior.
Having a 17-yo is a tough age for every parent I know, but it's even harder for us who have BPD17s. Hang in there!