Since she's still little and a light morph, you can try candling her tail by holding a bright light behind it to check for hemipenes. You could also possibly have a local breeder, reptile store, or reptile vet pop her for you. Another option you might be able to try is counting the scales on the tail. Looks like the very tip is missing, so you might have to wait for the next shed. Size is primarily determined by feeding schedule and genetics - sex doesn't seem to have a part in determining size for corn snakes. But since you have no breeding plans for her, she won't mind if you call her by the wrong gender.
