My daddy slept all the time. He would be exhausted by the end of the day. Then after 30 minutes in bed he was ready to get up! yes one of those cycles. Finally I had to make a rule of when he could get up cuz he was confused. He would still get up and get dressed and tell me that "outside" was lying to him. I told him he could not have the volume up on the TV before he saw me. So that helped. But he would just go from the bed to the chair and sleep. He would get up and walk around but his osteopenia was so bad walking around only lasted about five minutes at a time. The furthest he walked was from his chair to the mail box. about 60 feet in total. He then forgot about the mail and didn't even do that.
It is normal to sleep more and more with aging whether person has dementia or not. Appetite also slows. Look up information on aging online as regards sleep, eating, and etc.
How old is she?