Cats will sneeze and get snuffy or might have reddened eyes because of allergies, upper respiratory infections, colds....
If there is mucus from the nose or eyes, she has an infection and you need to see the vet for antibiotics.
If you suspect allergies are the cause, you should try to eliminate (or reduce) dust and dirt in the home, stop using carpet powders and get rid of other allergens that might be the culprit.
You might also want to talk with your vet about using an antihistamine to help during allergy season.
For tonight, you can use pediatric nasal saline (not adult!) in each nostril to help clear the mucus, if she has any.
I hope this helps!
Let me know if you have more questions.
