This is a very tough situation -- but there is help.
First, you need to talk with the doctors at the hospital concerning whether she has the mental capacity to sign a durable power of attorney. This document would allow you to manage her financial affairs on her behalf -- but only if she is willing to give you that authority. If the doctors say that she is incapacitated, you will need to go to court to get guardianship.
Once you have this information, I strongly suggest that you contact a local elder law attorney concerning the next steps. I also STRONGLY encourage you to contact your local chapter of the Alzheimer's Association -- they have terrific services and support groups. (The national hotline is 1.800.272.3900)