Reddit mentions of Spain: 61 Fascinating Facts For Kids

First of all, tell your niece she is amazing and will always be welcome in our land! (everybody is welcome, but she is even more welcome) ;)

In second place, and as an andalusian, I'm kind of "dissapointed" because most of the items are andalusians, and Spain is much more than Andalusia. Maybe you could try to purchase a book about Spain for kids along with all the items you said. Otherwise you'll end up buying tons of things, and this way you get your niece satisfied and introduced into lectures!