I am sorry for the pain you and your wife are feeling right now and can definitely relate. A couple of years ago my then 15 year old daughter swallowed too many extra strength tylenol. I managed to convince her to let me take her to the ER where they determined that it wasn't enough to have to pump her stomach or give her any anti-poison (or whatever it's called) treatment. However, the ER doctor considered it a suicide attempt and he had her Baker acted meaning mandatory pediatric psychiatric unit for a few days. She had shown no signs of depression or anxiety and kept insisting her only problem was that her boyfriend was treating her badly. She had always been a challenging child and I am convinced she is on the milder side of the attachment disorder spectrum (internationally adopted at 8 months). BUT, there were not signs of depression, some issues with outbursts of rage and definitely impulsive.
She had also always refused therapy, but I told her that it was part of the hospital releasing her that I would assure she got follow up. They also released with a prescription of prozac which we never filled. She cooperated in therapy for about 6 sessions and then refused to go anymore. I wish she had continued.
She has had no other attempts or even any cutting (she had cut on a couple of occasions before that). And although she has tried just about all the high risk behaviors, she seems to be doing ok now.
I hope the best for your daughter and both of you. Try to get her help and also get your own counselor if you can. I have gone off and on for therapy ever since she has been about 11 and it has gotten me through many "what have I done wrong with my daughter?" time periods.