Oh heavens NanaRayna I know exactly where you are coming from, but your story is far worse than mine, and I thought mine was bad enough .....
My eldest at 25 turned out surprisingly to be VERY clever, and despite having 1 GCSE in Drama, was given 5 unconditional offers to go to do a Masters Degree in Equine Science, a subject in which she is very passionate ... she did her first year and got a 1st overall, boy was I proud of her!
Then, it turns out that she hadn't actually sat the initial exams and she had to do them late because she had seriously panicked about it all and the pressure was too much - she then made some suicide attempts - tried to get her some help - seems it has been going on since Jan 2018 .... to cut a long story very short she has deferred Uni and come back home - now we could never live together before, we are too alike, but I was backed into a corner as there is nowhere else for her to go - she has actually been working which is good, although as she doesn't drive (although she has a car which has now been losing money daily in depreciation for 2 years) I have to get up at 5.30am to take her there .... and that is ALL she does, other than scream and shout at me at the top of her voice. She has been seen by 2 Psychiatrists who seem to think there is nothing wrong with her, not even mild depression, but she acts like a toddler, even threw my shopping at a cashier in Waitrose missing him by a whisker, then refused to get out of my car assaulting me in the process! She acts irrationally, is evil with her language and I want her gone! If i ever want her to do something she doesn't want to do, the answer I get is "well I will kill myself then, that is what you want, me dead". She has made 8 or 9 attempts now by generally stealing my medication or stashing it and taking it all at once, but as a 'scientist' and being clever, she hasn't made a 'good attempt' as it were which to me means a cry for help - but when offered it she won't take it! She has been here 6 months now and NOTHING has changed, she hasn't moved forward at all, gets no treatment etc ... As you say she is taking the little bit of peace I have left, I am not well anyway, and because I feel so bad I am not looking after myself - forget to take my insulin and my meds, am not interested in doing anything in the house as she is there, in bed doing nothing - I feel as though she is killing me slowly., in fact both my kids are. They seem to resent me being ill, will not help me at all, and the other has banned me from my granddaughter, which I knew she would at some point, even before the little one was born. I did my best with my girls but it seems that it wasn't good enough as I wasn't able to do as much because of my deteriorating health etc and had to leave them with their father as I was unable to cope with their behaviours sadly .... it is horrible as they both have physically as well as verbally and mentally abused me, I have nothing to look forward to in life and actually I would find it very easy to give in very soon ....