The quickest way would be to put a large plastic box in the cage. The box should have wood pellets (different than shavings) in it and then top the wood pellets with hay. I think you will find that your bunny will hop right in the box with the yummy hay.
We can't stress enough how much more odor absorbing are the wood pellets. You should see immediate improvement.
If you need to, let your mom know that you've been learning better ways to get rid of the odor. All you need is a cheap plastic box from wal-mart (about $5) and the pellets (about $5). [Measure your cage from front to back (inside measurement) to see how large of a box can fit. Ideally, it will span from front to back along one side of your cage.]
Here is that link again (which you can even show your mom if it helps).