Hello, German here.
It's not really a great difference to your usual food, I think (of course, it always depends on the individual family's preferances).
What you definitely should know is that in Germany, we are very fond of bread and eat it in a large variety of shapes and flavors. So it might be good if you could provide more than one type of bread for her to choose. I suggest white bread (for toasting) and a nice brown rye bread, maybe with a few seeds on top.
Popular toppings for bread are mild cheese, bologna, salami and sweet spreads (like Nutella, honey and jam).
She may or may not prefer to butter her bread.
Popular fruits are mostly bananas, apples and strawberries.
Popular vegetables are tomatoes and cucumber.
I hope this helps.