Haley Rosie, Assuming the litter box is clean, her cat could be doing this in a natural attempt to cover her litter. I know that some of my furkids will try to cover their litter, after covering it within the box, by scraping outside the litter box, even though there is nothing there to cover with. -they only go through the motions. I have found this is more so when the litter box is too small for the size of the cat.

..........wayne