How can I retrain an adult cat to bury her solid waste in the litter?

Often cats will try to bury a smell that they don't like. You could try spraying it with something to make her want to bury it. And also the covered litter box is a great idea. I have one myself and I love that it puts it out of view, but make sure that just because you don't see it doesn't mean you forget to change it! Lol. :P