Hmm, I'd say so. Sometimes cats just tend to miss but I would keep an eye out to see if she is doing it frequently as it could indicate problems. It could mean that she isn't happy with her litter box for whatever reason. Cats are picky little buggers sometimes about what litter you use, ect. If she keeps doing it you might want to take her to the vet as it could be indicative of a medical problem. Have you changed litter recently?