That's probably too much information - and I hope none of it came across as bragging - but it does feel good to talk honestly about my child. Even at the "gifted" school, I often find myself downplaying her "gifts" to other parents.
Please feel free to tell us any of your DD's achievements (academic and otherwise). We all love hearing these stories. In fact, we even have an "ultimate brag thread" for brags big and small. This is a place to feel comfortable talking about your child's successes. It is like a family that understands. We have all been there, feeling uncomfortable saying anything about the most hilarious or amazing thing our DC said, so we keep it to ourselves. But not here! Brags are welcome here. It is really sad when you cannot act naturally (i.e., talk about your child) around people at the gifted school.
Your DD sounds a lot like my DS - flitting from one interest to another. What is she into now? Here, it's Harry Potter and making up spells. And I remember the sneak reading of emails too. That's cool that she's so into numbers too! I know a lot of people here with mathy kids have suggested dice games, or adding dice to other games (like dice with chutes and ladders, where you can add or subtract the 2 dice to get in a better position).
Have you read Ruf's levels of giftedness? Teaching yourself to read/early reading is a sign of HG children. (Her website appears to be down at the moment, so I cannot link, but she has descriptions of preschool behaviors of gifted children, from what she describes as levels 1-5.)
I even made my mom read the book and she felt the same.