I was suspicious that my husband had a form of dementia back in 2002. Primary doc sent us to a neurologist who did a mental status exam and felt there was nothing wrong. I knew there was something wrong or I would not have brought him! (I have read that, highly educated individuals have scored high on mental status exams even though they do have Alzheimer's disease.) An MRI was ordered and we were told that there was nothing wrong. At the time we were both relieved and went on our merry way. I wish I had known then what I know now. That it is best to start on the meds sooner than later. It is supposed to slow down the progression sooner. By 2003, I insisted that the primary doctor, prescribe Aricept, which he did. By 2004, went to a different neurologist who did tests and MRI. And said my husband had all the symptoms of alzheimer's and he added namenda and cerefolin to the aricept. I believe that WE know our family member better than any doctor and WE know if they are declining cognitively and losing their memory. I am better than any mental status exam (which takes what - five minutes) to know that my family member is having memory problems! All I can say that Alzheimer's is a diagnosis no one wants to hear. I accepted the doctor's misdiagnosis, because I didn't want it to be true. But it is really important to know and to let your Mom know that she needs to have another opinion, because it is really important to get on the meds, sooner than later.
I truly wish for your mother and yourself and your family, that her doctor is correct and she doesn't have alz or dementia. I'm just saying from my own experience (I wish I knew then, what I know now) that doctors often don't detect this early on and if we in the family feel there is a problem, we need to be an advocate for our loved ones and help to guide and make sure they get second and third opinions. I always have to remind my self - that's it's the PRACTICE of medicine, we are dealing with. Not every doctor is right all the time. I don't mean to sound harsh, because I know this can be scary for all the family, I just want your Mom to settle for one doctors opinion when she deserves to have another. All the best.