What To Say To A Co Worker Who Might Have Narcolepsy And Always Falls Asleep During Work?

I work with a woman who constantly falls asleep while working. She even falls asleep at the fax or copy machine. She snores and her head almost hits her desk and even falls asleep while people are talking to her. I think theres something really wrong and she won't mention it to her doctor and even canceled the sleep study. What can be done or said to help her realize she has a problem without her getting offended or mad? She has an awful temper and because she sleeps half the day, I end up doing all her work.