Some people here need to realise that there have been games around for a lot longer than they think. It was mentioned that WASD has been standard for the last 10 years, yup maybe but for the 20 years before that it was the arrow keys, kinda shows my age but ho hum.
Certain things are easier on the arrow keys and certain things are easier on WASD.
My advice teach her a couple of games, one using WASD and one using the arrow keys, that way when she is old enough to get to grips with remapping the keys she will be perfectly capable of using either or some other bizarre combination.
My self I play minecraft using the arrow keys, but world of tanks using WASD.
Anyone saying that one or the other is wrong, in my opinion is just wrong themselves.
I suppose it is the whole spectrum/commodore, Atari/Amiga, PC/MAC, playstation/Xbox, android/IOS thing taken to a new level.
Have you considered if you are going to teach her inverted or none inverted yet?
Now that is a good question