I must put a lock on my Mom's bedroom door while working. has toilet, fridge & food. Is this OK?

I am the sole caretaker for mother and used all help eligible for her. Mother has beginnings of dementia and cannot be left to roam around house. We have a TV, Potty chair, dorm fridge, bed and recliner in her room. She has things to eats & drink, a phone, a life alert button and everything she needs to be comfortable in her room, but not wander and get into things that can seriously harm her or she can get outside to get lost or hurt. Is this against the law?