I think you would have to ask the doctor about the medication if it exists. However, changing the sleeping pattern is something an afvanced Alzheimer's patient will do. My father-in-law may be at this point yet but he is sort of ok except that he could get up very early at 6am if he goes to bed too early like 7pm!
This is part of the disease that they alter the sleeping pattern or wake up time. They have no idea it is day or night. You need to care for her when she is up. If you need to sleep, hire some caregiver or get someone else to take turns to take care of her. I imagine that she cannot be alone so someone has to be there. It is not a good idea to force her to sleep or change her pattern. I believe unless it is necessary, the sleeping pills or any pills for psychiatry is bad for her. Just my 2 cents. Usually the nursing home may try to force the patient to sleep. But if you love her, you don't want to force her into the regular schedule.

Just my 2 cents,

Nina