Hi. I'm online and happy to answer your question today.
It is possible that the white pupil reflex is occurring when her optic nerve is lined up with the camera/persons eye who is looking at her. This is a common occurrence -- even happened in my first born son, who got an emergency visit to a pediatric ophthalmologist because I was afraid, as a retina specialist, of what I might find.
If your granddaughter has been examined by two separate pediatric ophthalmologist with the chief complaint of a white pupillary reflex, and nothing was found, then I believe that she is fine.
If you are still concerned and would like a third opinion I would suggest having her examined by a retina specialist. A retina doc deals exclusively with diseases of the retina an vitreous and, if she doesn't find any significant abnormalities, you can rest easy that what you and the screening pediatrician are noticing is a reflection off your granddaughters optic nerve and not a retinoblastoma etc.
Does this make sense to you?
I see that you are typing and that could mean a couple of things: 1. you are actually typing or, 2, the chat system has frozen up. I'll give it a few more minutes and if I've not seen anything from you I'll switch over to the Q&A system. That system works a lot like 'text messaging' but, unlike the chat system, it almost never freezes up. We can continue to work on your question there. :o)