I Don't Remember That I Don't Remember

On more days than not, Alzheimer's Disease has reduced my mother's mental capacity to that of a child. On the occasional days when she is more adult-like than child-like she says, "Don't worry about me, I don't know it so don't feel bad. I don't remember that I don't remember."

But I remember that she doesn't remember. It is distressing, saddening, maddening, frustrating, and exhausting. If she is currently a stage V, that means that she still has two or three stages left and it will get considerably more devastating. Her doctor told me to prepare myself.

How?