Many cats go through the motions of covering their food by scratching or pawing around the bowl in a simulation of digging. They’re not actually putting dirt over their food, of course. An instinct just has them acting as if they are.
A cat who does this is not neurotic. She’s acting on a genetically encoded message to protect her provisions from scavengers. Scientists call it caching.
Miming the hiding of food is also about survival. If a predator doesn’t see or smell food that a cat might eat, he won’t assume there’s a cat around to feed on. Big cats in the wild actually do hide their food for that reason.
As long as the cat is not putting scratches into your floor or driving herself crazy with the gesture, don’t worry about it. If you feel her habit is compulsive enough to interfere with her quality of life, pick up her food bowl between feedings so she won’t feel driven to protect its contents.