I'm sorry if I missed this but is your DD the only non-white person in your family too or are you all/some of you at home non-white also?
If she has family to go back to at home daily then that will mean that, even though she is surrounded by people who don't look like her, she will have people at home who look like her, making her feel more "normal". One big risk with children growing up in racial isolation is that they think there is something wrong with their hair/skin and no amount of reassurance can make the surrounding people look like you and give you that physical reassurance. This is what adults who have grown up like this say - this isn't me saying that. Children can feel they are actually deformed for this reason.
Also, don't underestimate the really annoying "being stared at" and "ooh you're so special" ALL THE TIME. Being singled out in a positive way is wearing too. Again, adults who've grown up like this say this, and from a personal point of view I've lived somewhere (as an adult) where I was the only white person in a town of several thousand and it's just tedious to be pointed out/have people ask odd questions all the time. And that's as an adult with the mental resources to deal with it - you're talking about a small child.
My DC are adopted and one of them is not white. We live in a relatively mixed town in the NW of England and the school is 25% not White British (though some of those who aren't, are Eastern European/Mediterranean etc so are White of course). But at school not everyone looks like us (me, DH and the other DC), some of them look like my DC. So there are people who look like them so that they do not feel "weird".
We obviously would not live anywhere where our DC would have racist remarks directed at them (as far as you can avoid this altogether - we also need to make sure we prepare our DC for things like 'your skin is dirty' and make sure they know to tell us about anything that makes them uncomfortable), but we also wouldn't live anywhere that our DC was in a minority of one as that is just not fair on them.