First of all, Kathy I am SO SORRY that your difficult child seems to be stuck in life at the emotional age of a teenager and that she tried such a stupid and dangerous thing as to do what she did today. It is really really awful to be in your situation. You have worked to provide everything you can for her and to help her.
I find it very stupid on the part of EMS to act like YOU were the problem. Around here they have a LOT more experience with people with sub abuse and the manipulation that they use to get their way. Your difficult child seems to cling to being dependent and it is a super hard thing to push your child to be independent. Also not natural - part of being a teen is separating from your parents and being awful enough Occupational Therapist (OT) them that they are okay with you separating somewhat so that you can be an independent person. Your daughter seems to be stuck at a much younger developmental age, one where living at home is more "normal" than it is at 26.
Of course you had to do what you did today. No choice but to call 911, esp when she was in your garage. She sure seems to want to push this to extremes.
I don't know what the alanon meetings that you are attending are about. Here you do talk about the readings, but we also share our experiences and talk through hwo we think we should have handled them. After the meeting it is pretty usual to go get coffee and talk about personal things if there wasn't time in the meetings. What y'all are describing as alanon meetings is what goes on at a lunch meeting, one that is less than an hour long - usually 35-45 min and you don't go into personal stuff. but not all alanon meetings are like what you have experienced. It is why they suggest going to meetings at different times and places - each meeting has a dynamic and pattern of its' own and many are NOT what you are describing. At least most of the ones I have gone to, in three states, are very different.
So there may be hope. But of course alanon is not for everyone, just like nothing else is for everyone. Kathy, you might get a lot more benefit from a therapist of some kind.
I am so osrry that things are so hard. It is really hard to learn to detach, esp when your child is so determined to attach and almost return to the nest the way yours is. Have you ever discussed why she wants to return home so bad that she would do all this stuff to try to pressure you into it? I know she has had some bad situations, and that it sure is a lot easier to live at home than to work and pay bills and do all the hard, boring stuff that is part of living on your own. I don't need to know the answers, I just think maybe if you knew why she wanted to live at home so much then you could make living at home seem less desireable in some way,a nd maybe lessen her attempts to return home. I find it truly strange that a 26yo wants to move back home so desperately.
I do hope you let the halfway house know about her antics today.
This last thought might not be popular. I know you have agreed to give her gas and let her have the car. If the car is in your name, consider taking it away. Or at least not providing gas for her anymore. IF she is going to use it to attempt to kill herself, then it is a weapon and she needs to not have it. If it is in your name, take it and sell it. Let her be stranded at the halfway house and have to get rides or walk to meetings. Let her know you believe she is capable of handling things with-o a car and that you cannot allow her to have the car since she tried to use it to kill herself in your garage. I know it sounds harsh, but the car is giving her a lot of freedom to come and harrass you. It is also the weapon she chose to use to try to kill herself - regardless of if she was serious or not.
Of course these are my ideas/experiences. I am NOT in your situation today, and can't say I would do this if I was. So I totally understand if you choose some other way to handle all of this. I will support you and listen if/when you need to talk. I am so sorry that your daughter chose to do all of this today, and that you are hurting so much.