I'd go for the mirror trick. If you look in a mirror in your dream, it will appear quite distorted.

And with math, yes if you do math in your dream, your answers will be right if you are good at math. Your mind still works quite well when you are dreaming. It's what's producing the dreams.

You could have a sleep study done. She can find out if her sleep pattern is odd with respect to her brain wave states when she's asleep, which may be causing some of the problems.