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Hello. Thanks for the question.
I would worry that she may have detached her retina or hypertension caused acute blindness in that eye. The dilation of the eye is the body trying to let more light in.
A good retinal exam is needed to find out what happened. I would have this done tonight with an ER vet or tomorrow with your regular vet. The sooner the better to get on blood pressure meds to try to get the retina to come back. It's a bit of a long shot to get vision to return, but we sometimes get lucky and it will come back.
I hope this helps, let me know if you have any other questions.