First, she is lovely! I am so sorry this has happened, but wonder if more sight might come back. If she sees shadows, that is something that can be worked with.
My very beloved mare T lost most of her sight over 5 year period due to ERU. She adjusted so well, and navigated her pasture (trees, hills and buildings) and trails so you'd never know that it was only shadows she saw.
Finally, all in one day, she lost it all. Total darkness. My calm, confident mare became fearful and was injuring herself. She was rock steady under saddle , but I could feel the slight hesitation with each step. After 7 weeks of trying to help her adjust to darkness, I had to admit that I could not keep her safe, and it wasn't fair to her to live in fear.
My point is simply, if she sees shadows and can find her water and food, perhaps she can be in a smaller paddock area to navigate around safely. At 6 she has many years ahead, to be a brood mare, or to ride in the arena. Sounds like her temperament would help her take the changes in stride. Most horses adjust well to blindness, about 5% never do, and my T was in that category
Tough decision all around, but I think a solution can be found. You have so much on your plate, with husband injured and extra work load on your shoulders. I think you'll find what will work best for all, just need a bit of time to process and evaluate.
Please know you are in my thoughts and keep us posted.