Get Your Cat Care Questions Answered By Cat Vets ASAP
The Kitty's eyes with the pupils so enlarged means that there is something emotionaly that has aroused your cats attention, something very appealing, or something is that threatening.
I will assume since she is not spayed that this may be the onset of her heat cycle that has aroused her senses. Cats eyes can go into a full blown pupil in a matter of seconds. I would not worry about this if there is no discharge, or nictating membrane showing.
I do want to add that if the pupils stay dilated for any period of time I would have your baby into the Vet for a check on Feline Hypertension. This would be the other reason for extended periods of enlarged pupils. Joan