If possible, meet with or speak with her physician, rather than just sending a letter, to make sure there aren’t any concerns (medications, physical limitations, contraindicated exercises) you. Also, it will enable you to get a clear understanding of the actions you should take should a sleep-episode occur during a workout.
I had an 83 year old client who had it and would actually fall asleep on the upright chest press machine in the middle of a set. It was awkward, I would practically yell “Okay, on to the next exercise!”, and he would wake up confused with a look on his face like “We’re done with this already?” He was a true badass though in WWII. He was a German Jew who stayed behind enemy lines working for the OSS(predecessor to the CIA) making fake papers for Jews and others so they could leave Nazi Germany. Nerves of steel.
Mike Campbell RTS
I have not trained someone with this but my mother had narcolepsy. There are a couple of basic things I would suggest.
First, recognize that there are some risks. It is wonderful that you want to continue with her, and good for her overall health to continue with you. However, she is right that the cataleptic piece could create the possibility for injury. Moreover there is a brain effect that could affect the training relationship. And there is the possibility of her falling asleep as she works with you. My mom would fall asleep in the middle of reading us a book.
I would suggest you do some research with the sleep foundation.org (I think that is right) and get some basic information on the condition. Then, send a letter to her physician outlining what you have done with her, and asking for feedback on whether training would continue to be helpful for her and what sort of adaptations they would recommend. Also find out what medication she will be on and what the side effects might be. Some of the meds do have effects which you might want to watch. You might also want to consider extra CEC training on special populations to help bolster your professional credentialing, if you do not already have some specialty certification.