If your mother will agree to sign a Health Care Surrogate document (a medical power of attorney, in broad terms), this might work. However, from your description of her mental status, she likely would not agree to this. You may also wish to consider seeking guardianship of your mother although this option would involve court hearings and may not be time effective. Sometimes psychiatric facilities will, in such circumstances, obtain information from you which might be useful in treatment, even if they can't give information to you.
Sincere best wishes to you and your mother.
