A dictionary is on the cards. I think she is at the age where she will have some fun with one. What is interesting with Finnish is that the language is phonetic - there are no spelling tests here.
One of my Finnish friends lived in the US for a bit when she was pre-teen, and while she couldn't speak English that well at the time, never spelled words she had read incorrectly. She would read them "as a Finn" so the spelling was clear :)
Well, there is a reason for the weirdness of English. I recommend The History of English podcast once she's a few years older. It ties together history, language, literature, and more.
In short, a lot of spellings are left over from when that was the phonetic spelling.