Beautiful tribute and I can tell your heart is breaking. People who don't own horses or dogs or cats or other animals can never truly understand the attachment we have to them. These animals are entrusted to our care. They are entirely dependent upon us for all their needs, and we all give them everything we can. When I lost one of my beloved riding horses due to colic, I felt so bereft I cried for days. If anyone seeing me in my grief had said, "Come on, now. It's only a horse. It's not like you lost a child" I think I would have punched them.
The pain is so intense, so real, and so terrible that only someone who has experienced it can really understand the extreme toll it takes on us. I know how much you are aching. Time really does make the ache less intense. Right now those images of her last breaths are seared into your mind, but in time, the other images will be there more often than the worst ones. The images of her blazing through the pasture, and that throaty whinny, and all the other things which so endeared her to you. In time, the ache won't be so strong, but for now there's nothing you can do but mourn your beloved friend, and I think we all understand that. I'm just so, so sorry!