Is she spayed? If not then I would definitely recommend getting that done! Full litter box training is usually not possible until buns are castrated.
Unfortunately many buns will pee on soft things (like beds and blankets), and dig boxes are remarkably similar to litter boxes from a bun’s point of view.
I think removing the grate was the way to go, most buns hate them and they are hard on their feet. For my buns, I use a layer of pine pellets topped with a fluffy layer of hay. For buns that are especially picky, using a soft bedding like carefresh seems to help a lot. You can do a layer of it over pine pellets to be a bit more economical because carefresh can be a bit expensive.
I’ve found the key is to make the litter box enticing and easy to jump in, so soft bedding, fluffy hay, and sides that aren’t too high. Basically make it easier and more tempting for them to just hop in. I had one bun that couldn’t have any blankets on the same level as her litter box though as she would pee on them, but did ok with them stretched tight over the upper levels of her condo. Also making sure the litter box is large! Some buns will also pee anywhere they eat hay, so setting up the box so they can only reach their hay while sitting in the box helps.
For now it will likely help to remove all the blankets etc., cardboard with a few grass mats makes a good temporary cage liner.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.