stropps I hope this doesn't sound silly but given that discussions tend to end in shouting or stonewalling, when you're at your DMs tonight, in a quiet moment, write a letter to DD and set out your terms going forward. This feels particularly hard, now I think about it as we're supposed to have unconditional love for our children and now it's becoming conditional. But, tough love is not about losing love, it's about somehow keeping it but not accepting the unacceptable.
Write to her and tell her that the deal is she continues to stay home and either goes to school or gets a job ( full time if not studying). In either scenario this will work unless she adversely affects the life of the other family members. Then, she will need to find a place of her own in this case, or if she refuses to do either of the above options.
You may or may not give her the letter but even if not, it might clarify things in your mind. One of my DSis's screwed up her A levels and got into a lot of trouble. She moved out into some squat -like hovel and worked on a market stall and in a pub, before sorting herself out. Im not sure to this day what role my parents had in it though. She didn't have MH issues but was probably doing a fair number of drugs.
What ever you decide, I send my love and lots of hugs xxx
My mouth is still sore but marginally better, and I'm going to buy an electric toothbrush. Tonight I am very much looking forward to going to my lovely NDN's book launch which is being hosted by her published, Macmillan.
. Really pleased for her!