LOL Bam!
I have actually given Meadow an old pair of my son’s (too-small) jeans years ago (when she was still unspayed) because she would dig at them and it protected our carpet… briefly. She ONLY had access to them when she was out playing AND I was supervising. They were never left in her pen. And they were a whole pair of jean with no loose strands or frayed bits. She never chewed at them, only dug on the fabric. If she would have started chewing it, I would have taken them from her because of the danger of ingesting long strands of fabric.
It sounds like your friend isn’t the greatest rabbit keeper… according to you: no vet care, questionable home health remedies, inappropriate housing, etc… It does not seem like she would adequately supervise her bunny with fabric, so I would recommend NOT including anything that can be harmful in the toys. Keep to cardboard, willow toys, etc…