This is more devastating than anything I've recently read from you, and maybe because you go into more specifics here, and it also is a different kind of love, a different intensity than what I'm used to. I read the "I envy that" in the second stanza in almost a whisper, that forgetting can sometimes lessen the pain since it can't be acknowledged in the first place, but those who do remember, carry that loss continually with them. At the same time, it's heartbreaking, yet utterly human, to envy that loss of memory, because you just want the pain to be mitigated. There is such a heaviness in this, and I don't think there are ever any easy answers or ways to do things. My grandmother had dementia, and my mom visited every week from out of state, and it hurts her still to know she was one of the few family members who made that effort. We were homeschooled and went with her, working on our assignments and not really realizing what it meant. But I also realize how quickly we can judge others when the emotions may be too overwhelming or complicated for them to sort out, and that a visit is more emotionally-tolling when one can't necessarily be prepared for this or act like it doesn't affect them. That soft plea in the last line, that "somehow" that emphasizes a miracle or a hope you know is not likely, is emotional, almost reading like a prayer, for some kind of healing even if it's a simple moment of remembering. And the kind of sacred moment when a memory/taste/moment IS remembered, that makes it all the more painful too.
Second line of first stanza: "it's" should be "it" I believe.