I'm glad you are here and have been able to find others in similar situations, at least you can feel no longer alone.
Several times you have said "we". I'm hoping this means you have someone such as a partner plus your other daughter in your life who, like you, feel as badly and would give anything to make matters better. Facing such adversity together is a boon.
Sadly I can't see a straightforward path and my immediate concern is for you, and hte rest of the 'we'. There is a very strong force that makes one feel frustration, powerless and guilt. It can fill the world with 'if onlys' and simply leave one lost with small hope of better.
So may I ask what support you all have? Family of friends to talk frankly with and feel cared for, medical support though a GP or psychologist, a parents/carers group who have the same problems?
Also what do you do for yourselves -go to the movies, read quietly, play with pets ...? I'm only guessing what might attract you, give you enjoyment and respite for your situation. I'm in different circumstances to you but I try to have one thing to look forward to all day until evening arrives. My self-reward is reading.
It really is necessary, even if you think I'm concentrating on you rather than options for her. You deserve reward and that can percolate in when you give yourself you-time. It result is (at least in my case) a more balanced and happier person.
That person is in a better position to deal with your daughter's behaviour and illness, and while you are in a better calmer place this can have subtle influence on her.
I do not know of great deal you can do to meet each form of her behavior, only show love -and be as vigilant as is practical that she is not in real danger. Her medical team may be better placed to assist her.
I guess for me hope would rest with that calmer love, circumstances and her medical team.
Please feel free to come here anytime, you'll be welcome