Those products are meant to be used in cat litter boxes. If you actually lean down and sniff my box when it is time to change it it smells of urine, but then how could it not. However, as I said you literally have to smell the box, and that’s with two rabbits using it. I really wouldn’t worry, … I have a very sensitive sense of smell, and none of my rabbits have ever smelt unpleasant, … either the rabbits themselves or their living space. Hope this helps your mother feel better.
Important though, don’t use scented litter since that puts some rabbits off. An unscented litter like Yesterday’s News works very well. While not a substitute for the litter a layer of hay in the box encourages good litter habits and (I find anyway) does absorb any excess odour. Although if your rabbit is so young that it is still with its mother then it will probably be a little while before you can litter train it.
Good luck and I hope everything goes smoothly. Look forward to hearing about your new family member!