Oh no!!! I'm so sorry this happened to your daughter...
Unfortunately, as Karan mentioned, it's almost impossible to repair. Acrylic needs straight cuts to be able to be glued.
If you're so inclined, you can look at using Weld-On 16. There are a few good Youtube videos on how to use it. But they all mention that the acrylic should be as straight as possible. You might be able to get some sort of fix, not aquarium worthy but then GoPiGo does not have to be water tight. The results will very much depend on the edges of the breakage, and your tolerance for imperfections. It will not be a clean fix by all means and might not even work out at all.