Originally Posted by
Tucane
Note that i'm not assuming there's something wrong with your sister:)
Does your sister have narcolepsy? That is the only known way to instantly enter REM-dreams without preparation. It could also be a case of medical REM-atonia, although it itself won't explain the induction speed.
I believe that it's a case of strong daydreaming/visualisation-skills, which result in vivid NREM-dreams.
My 2 cents, Tucane
Forgot to say that DEILD produces superfast lucids, but it has to be done instantly upon waking up... and that was the third cent.