For what it’s worth: I, too, think that euthanizing this horse is the right call. I have not seen the videos; I base that on the fact that multiple pros have declined to work with her and the opinions of the posters here I respect who have seen the videos.
With that said, gently, with full understanding of these feelings:
… I do believe the OP is real, and I do understand why this thread is still going: OP is struggling to re-align her entire worldview, and we’re watching that unfold in real time. I think it’s perfectly fair for posters to bow out when they’ve had enough, because this isn’t a fun activity for anyone, but I would encourage the good, caring folks here to give OP the time and space to process in this thread without turning on her.
When I euthanized my neuro mare, I did so because she had an increasingly poor quality of life and was becoming increasingly unsafe to handle on the ground. (I was doing the daily care and any professionals working with her were aware of the situation.) I didn’t ask COTH for help because I had a large quantity of excellent and trusted professionals around me with whom I could discuss as well as other sources of emotional and decisional support. That said, if I hadn’t been in that fortunate position, I might well have posted, and if I had posted when I was at the “just hurt me, will never be ridden again” stage instead of the “has been retired for a bit, clinical picture worsening even as a pasture ornament” stage, the external processing might have borne some resemblance to what OP is doing here.
While my mare was ultimately not a behavioral euth, I did euthanize her for her behavior, because of what it signaled. At the time I sat down in a stall at New Bolton with her and stroked her face and whispered to her while she went, I had no certainty that there would actually be a confirmed EDM diagnosis.
In the end, there was a confirmed diagnosis. I was as happy about that as I could be, under the circumstances. But I knew that there was a chance there wouldn’t be, and I made my peace with that possibility before I did it, because if there hadn’t been it still would have been the right choice.
It took me a while to get there, though.
P.S.: No one brought up euth to me, either, until I described the behaviors and asked them for their opinion specifically noting that–while I would do anything I could for this mare–euth was on the table if there was nothing else to do. When I did, every single one of my multiple vets were not just supportive but agreed that it was absolutely the right choice, and none of the other pros I asked were unsupportive.