Is there any reason to believe that she was exposed to a cat with a cold? You're right that it doesn't sound like a cold, but assuming she's been vaccinated (the vaccination doesn't give them complete immunity against the various upper respiratory infections they can get), it could just be mild in severity. If it is a cold, you can generally let it just run its course unless her symptoms become problematic.

Short of a cold, she may have something stuck in her nose or a dental problem. How old is she and when was the last time she had her teeth checked/cleaned? If her sneezing continues, it couldn't hurt to take her to the vet for a checkup.