Is Fading Memory A Sign Of Alzheimer's?

My mom just revealed her worries that she has Alzheimers. She always tells me the same thing, and tends to ask me the same question she asked me a few minutes ago. At first I thought it was because she doesn't listen, but I realized that she really does forget. Is my mom likely to have Alzheimers soon? She's only 46, and I believe my grandpa had it as well.