Healthcare proxy rights

I'm this woman's healthcare proxy in my building. She is an 80yr old Korean woman that's been here for 50 years. She has literally no one so I'm trying to be here for this woman. They are keeping her in the hospital and telling me they can not elaborate as to why. The doctor has cleared her and said there is nothing more they can do. They say she has the beginning of dementia but in reality it is just forgetfulness as of now. I know this woman they don't. They are telling me they are keeping her until further notice. She initially went in because she has cancer but the cancer is too advanced to be treated any further they won't release her. I want to hire a lawyer if we can do something. Can they hold her there against her will after the doctor has cleared her and not say why?