How old is she now? I checked your profile but it’s not listed. First, it could be that she’s a teenager (beginning at 4-6 months) and her hormones are kicking in. It results in Terror Bunny, and she needs to be spayed ASAP. A month after the procedure her hormones will calm down for good.

Next, I would advise you to just remove the plastic mat and use something else instead. Seagrass mattes are pretty wide and several could cover a floor, but are edible so safe. Also, a low pile (cotton preferably if she’s a rug chewer) area rug with little or no color dye can be a good floor option. She will not learn to stop chewing inside her habitat by being told No. It just won’t stop her. Punishment in general has not lasting good effect, but can be counterproductive as when a bunny is deliberately being naughty and gets stubborn.

Mostly she is exploring and playing and being a bunny. So she chews, then explores as with the box spring. I think Mark’s Maryann was the queen of the box spring burrower. My own solution to that was to put a mattress cover upside down on the bottom of the box spring to add another layer to get through before being able to enter the box spring itself. Sprayed with a bit of vinegar and water to repel the bunny and she might find a better place to play. Watch out for underneath couches, too. One way to stop her from getting under couch, chair, or bed (or computer desk with wires) is to use NIC cubes and build a little fence around the bottom of furniture until she learns, gets too big or loses interest. I used to stuff a big sleeping bag or old comforter under the couch too so it blocked entrance and didn’t leave room to run around under. But that can be fun too.

See your vet to get her spayed right away if you can.