My 2 oldest girls and youngest boy are biracial. The oldest looks most like her dad, who is black. The next girl looks more like me, except with brown curly hair and something about the shape and color of her eyes (which don't really look like either of her parents.) My youngest boy looks like a darker version of his 2 older half brothers (my children from my first marriage who are hawaiian/japanese and caucasian) unless you look at his butt, then he looks just like his dad. When this came up for us, I asked my kids to show me where I was white. I'd get out a piece of paper and prove I don't have white skin. Then, no matter which child said something about us not looking alike, I'd say, "Don't be ridiculous! I think we look QUITE ALIKE!" I'd put him or her next to me and look at us in the mirror and claim to see no real difference at all. Now that I have a half german blondie, people comment how she looks like a blonde version of one of the older sisters... It's certainly true...
Of course, I come from a different part of the U.S. than you do, and being white isn't any advantage over here. A little is maybe about skin hue, but for the most part, it's about values. White people stole from the hawaiians and they are still steamed over it. They have aloha, but they also have a certain prejudice... My oldest daughter had the opportunity to go to Germany as a student for a couple of months last semester and ran into quite a few exchange students from the Altanta Georgia area and she said they EMBARRASSED HER the way they behaved so impolitely, showing no respect, that she had to differentiate herself from them, because people thought she was part of that larger group, some of whom were black or biracial, most of whom were white, all rude by Hawaiian standards.
I'm getting a little bit off topic here, sorry about that. What I wanted to point out is that there are MANY ways to approach~address this topic to a biracial child, and no matter what is said, s/he WILL FIGURE IT OUT IN A WAY THAT IS MEANINGFUL TO HIM OR HER. That's sort of what is going on already for your child, she's trying to classify herself and people she knows. I'm wondering how much emphasis is placed on color in general on the mainland... I know when I was still married to my ex and we travelled around the Pacific NW and went to churches w/his family, I was often the only caucasian person there. I pretended not to notice, which is what is polite over here in the islands. Nobody commented on me or my color except for a niece who is developmentally delayed.
Classifications go all over the place with small children, like her thinking her clitoris is a penis. My youngest called it that, too, it's all about figuring out who and what you are. It's an on-going process.