My 78 yr old husband sleeps well at night, but he no sooner gets up when he's in the chair sleeping, sometimes even before breakfast! He often sleeps after breakfast until nearly lunch, then after lunch until almost dinner. I try to get him out to do things, but he says he's too weak. He also has Parkinson's which isn't helping. I don't know what to do to help him.
What are the other 10 hours like? Is she getting some social interaction? A little gentle exercise? Some mental stimulation? I guess I'd focus more on the time she is awake.
If she has other symptoms that make you think she might be ill -- coughing, fever, continuous hiccups, rash, etc. -- then consult her doctor. But if she seems generally well I wouldn't try to waken her before she is ready.