mommy in training

I made a strawberry pie last night--super simple, I took some organic smoothie mix I had bought a long time ago (strawberry, kiwi, and banana), heated and pureed it, then added a little cornstarch. Then I sliced a bunch of strawberries into a cooked pie crust and covered them with the puree. Super simple, no sugar added. I then whipped some cream and added vanilla and granulated maple syrup, and ate a slice of pie with whipped cream. It was heavenly. So much so that I had some for breakfast and put the remaining whipped cream into my coffee.

When I packed lunch for Nina today for school, I decided that a slice of pie would be fine since it had no added sugar. When I picked her up I asked her if she had liked the pie. Imagine my surprise when she told me she hadn't eaten it. And when I asked her why, she told me that they had ice cream at school and if she had eaten the pie it would have been too much sugar.

Can someone explain this to me?