Thanks, mileage was another one I saw ("milage"), as well as some more "-our" words ("labour", "favour", "favourite", "behaviour", "misbehaviour"). I also saw immobilize ("immobilise"). She loves to speak in a British accent, though, so maybe studying both spellings would in a weird way actually help her remember the English one better. She is very creative, so I think this would use her mind in a way that she would enjoy.
Did you follow up Apples and Pears with something else through high school? What grades did you use Apples and Pears for?