I worked with Alzheimer's patients long time ago, and know this is a hard thing to deal with. I am so glad you are taking care of her. I am not sure of all the legalities, but you may need to start with her doctor for help. Also I believe every state has a board for the care of the elderly and they could help or your state or national Alzheimer's association. To declare a person incompetent usually requires a court hearing of sorts depending on the person and how bad the Alzheimers is. GOd bless.
How Can A Person With Alzheimer's Disease Be Declared Incompetent And The Legal Next Of Kin Obtain Power Of Attorney?
Get a lawyer, He'll do the paper work and file it.
Incompetence and forgetfulness are not the same. You may however obtain power of attorney if she agrees .