Sleeping schedule is mixed up

My mom has dementia and is in a memory care facility. Every time I go to see her, she is sound asleep, and even if I try, I cannot wake her up (if I do, she is very groggy, and our visit does not go great). When I ask staff about it, they report that she is often up during the night. It sounds to me like she has her days and nights mixed up. What can I do, or what can I tell the facility, to help her get back on a normal sleep-wake schedule?