(Outing myself a bit here, but worth it, I think!) My DS has retinoblastoma (the condition linked to above), which is often first picked up by parents noticing a white pupil reflex in flash photos (like the normal red eye one, but white). Either an optician or a GP should be able to check your child out, but it's important that you ask them for a proper red reflex test, like the one described here. As PPs have said, retinoblastoma is very rare (so your child probably doesn't have it) - but this also means that most GPs and opticians won't ever see a case in their working lives, so it's helpful to let them know what exactly you're concerned about and how they can screen for it. Also, as other posters have said, there are other eye conditions (cataract, Coats' disease, etc.) which can produce a similar white eye effect, so it's worth ruling those out too.
Just for reference, the Childhood Eye Cancer Trust (who support families affected by retinoblastoma) have recently teamed up with Vision Express, so their opticians should be aware of the signs of retinoblastoma.
(Incidentally, Pacific, I wouldn't necessarily rely on taking another photo straight on in order to rule out the possibility of retinoblastoma, even if you get a normal red eye reflex doing this. My DS has bilateral retinoblastoma (multiple large tumours in each eye) and we still get the odd photo with red eye these days - it seems that the white eye reflex is very dependent on the the angle of the flash, position and size of the tumours, etc.)
Tortoise, I hope you've been able to take your DD to be seen and that it turned out to be your DH's crappy phone camera!