Actually there are white horses with pink skin. They're actually also called Dominant White. The only reason you know they are DW and not say a very light cremello (because yes sometimes it can be hard to tell) is because their eyes are brown. And you know they aren't greys is because the skin is pink.
So yes technically speaking, this one here would qualify as DW as per its features. But with that said I could see why Olivia saw it as a cremello (or was reminded of one) as the coat of that one (at least on my computer) is slightly creamish and cremellos can be very very light.
Either way, Miranda is happy with the horse, so it's all a win!!