For 22 hours a day, she kept sleeping, only waking in a dream-like trance to take a little food and drink and go to the toilet. Little is known about what triggers the sleep disorder and even less about how to cure it. At the moment, Beth is two-and-a half months into another deep sleep episode.
Nothing - not drugs, loud noises, pleading or cajoling - will wake her.
Over the past five years, Beth's mother, Janine, calculates that her daughter has been asleep 75 per cent of the time.
So her life is spent in pyjamas in bed or asleep on the sofa. On the rare occasions she leaves her home in Stockport, Cheshire, to see a doctor, she must be pushed in a wheelchair because she is too tired to walk.
All Janine can do is sit and wait desperately for the 'on' switch to flick back in her daughter's head.
'It is like night and day,' says Janine, 48. 'She might wake up tomorrow and then it's a race against time to live the life she should have had. She rushes off to catch up with her friends and get her hair done. But no one knows when she might fall asleep again.' Since her diagnosis, Beth has been asleep more than she has been awake, sleeping through many of her birthdays and Christmases, as well as holidays. When she wakes up, she has no recollection she was ill or realisation that time has moved on.
Beth's hopes of getting the four A-levels she needed to train to be a child psychologist faded as she was forced to drop out of college.
And Janine, a single mother, had to give up her job to look after her daughter round the clock.
Beth first started feeling exhausted as a 16-year-old and Janine assumed it was normal teenage torpor.
Then, one evening, Beth fell asleep on the couch and wouldn't wake up. When Janine tried to rouse her, she was horrified when Beth could only babble incoherently in the voice of a five-year-old.
One person who has stood by Beth is her boyfriend Dan a 25-year-old primary school teacher she met during an 'awake' phase three years ago.
He will come round and sit with her nearly every day, talk to her and wait for the girl he fell in love with to come back. When she is awake, they resume their normal adult relationship. He is a good man.'
Daily Mail UK