School can be really tough for kids with different brain functioning. Everybody is wired a bit differently, but if one's wiring is too far from the standard design, either from brain damage or genetics, a lot of our society just doesn't work well. And as you point out, what makes it even worse for kids is that often neither they nor the adults in their lives really understand what the problem is, so little or nothing helpful gets done about it. Given your experience, at least your kids are not going to be dealing with the kind of failure to understand that you suffered.
Anyway it sounds as though #3 is quite keen on her project, and may even have a bit of fun with it. I'll bet she gets some nice feedback about it, and that will firm up her confidence for the next time. I think she is doing a spectacular job for the age of 7, however, the closest I have to kids is my dog, so what would I know about it eh?
.
Please tell her that one of your internet friends thinks that she is doing really great with her project.