Hi OP I have been following this as although my DD is 10 she sounds similar (ASD, recent mental health breakdown, sort of tyrannical behaviour and separation anxiety from me.)
I can well imagine her like this at 19.
DD has been sat in bed watching Netflix shows for months (her MH problems were/are severe and significantly affected her physically - lack of food/fluids - so we ended up in this depressing state.)
I think she was in burnout and when we first tried to remove the screen, it was hours of violence and frightening self injurious behaviour. So we gave up. Focused on getting out once a day but still a lot of time on screens.
Anyway we have completely removed screens again this week and although the initial reaction was awful, it’s been great for her now. She still sat in bed most days but reading and then started engaging with her sister more to play with someone.
I really feel this ASD/“screens regulate them” idea is something I’m uncomfortable with. It’s a total out basically because life is tough.
What I’m trying to say I guess is with high anxiety ASD you get told low demand is the best route, and it often is until it isn’t if you know what I mean ! There’s a point where maybe they’re past burn out but just STUCK. Endlessly ruminating but they can and need to respond to strong boundaries.
Implementing these together with my DH has been really effective, I wonder when you lay down some new boundaries, if you do it together it will have even more impact.
I fully empathise with how challenging it is and my DD is still a child god help me. ! So acknowledge it’s infinitely harder when they’re older.
But I’ve started to be fairly brusque with the constant misery: “I’m so anxious/hate my life..”
”Aw dear, sounds tough, have you seen the cat? Does she need feeding again?”
and walking away when she is rude to me - and it is self preservation as my god, it’s hard not to get depressed yourself getting sucked into it. And they need to know it’s unpleasant to hear.
Anyway I know it’s very complex but wishing you luck, it certainly wears you down