Grandma Has Gone Insane
One of the "huh, that's weird" factors in EDSR is every monster you encounter just makes you a little bit more crazy, just like in real life! One's sanity meter goes down and must be replenished lest you want to play the game as though it was Jhonen Vasquez's latest nightmare. The sounds of Grandma wandering the hallways in some ancient dystopia are filled with the imagined screams of the innocent and the violent meeting of steel and stone.
Try working with THAT in the background.
Grandma has been able, so far, to figure out the puzzles relatively quickly- and the combat targeting system is subtle enough for her to master. Now it is simply a matter of finding every little thing in every level to make her happy. You will know when she isn't.