I have a cheap Asus Transformer Book that travels in my compendium. It's a laptop/tablet hybrid and has a 32GB eMMC instead of an SSD or HDD. It's a perfectly good little machine with a nice screen, strong frame, nice keyboard and decent battery life, but there isn't enough space to install Win 10 updates.
If you want a cheap Win 10 laptop, buy a refurbished machine with a big SSD.
For example:
https://www.amazon.com/Dell-Latitud...542465874&sr=8-14&keywords=refurbished+laptop
I agree with this about buying refurbished. I also think you should stick to the standard most of the rest of the world uses, in other words, Windows. Part of the education is going to be learning to use the computer itself. It is mostly likely what her school will use. And you are going to want a real keyboard to learn touch typing, another skill that wasn't offered to me when I was a kid.
BTW, imo, an SSD is going to be a big upgrade in the price that for the purpose you're looking for for this computer doesn't seem to be worth it to me.
Another thought. Does it really need to be a laptop? Portable means transporting, transporting by a six year old means it's going to be dropped. Drops are not good for computers.
I replaced the screen in my nephew's laptop for him. The very next day after he got it back, he dropped it again.