I’d probably get two of the large, heavy-duty, easy-fill web hay nets and have at least one of them full and in front of her door at all times if possible. So, when she’s emptied one, they can just unclip the empty, clip up the full, and be done. If you get the big ones and fill them to capacity, they should last her quite a while. Whenever you see an empty one, refill it yourself so it’s ready. Have the place to hang it right inside the door and it literally won’t take more than a matter of a few seconds to unsnap the old and clip on the new.
I take care of a mare that lives with my gelding, and she has the Smartpak slow-feed hay net with the “gator mouth” that makes it very easy to fill. I put a large, heavy-duty galvanized spring snap link clip on the rings of the hay net and just snap it to the ring in the stall. Easy-peasy. I have to take care of them in the morning before work, so time is of the essence. I feed hay outside on the ground most of the time, but if I know it’s going to be rainy in the morning I go ahead and fill their hay bags the night before. It literally takes no time to do hers. (Mine is a more aggravating model from a different company…I’m going to get one like hers eventually). And hers holds a LOT of hay.
Anyway, that’s my idea. I’d get two of those, stuff them to the max, and keep a full one handy at all times so they can be switched out easily as needed.