As you probably known, Alzheimer's disease is a degeneration in brain function that occurs in many elderly people, that progresses gradually and leads to significant impairment in social functioning and the ability to live independently. Although normal aging does sometimes result in some decline in capacity for new rapid learning and memory, these changes do not cause significant impairment and are much less pronounced than the changes caused by Alzheimer's.
Observations from family members like yourself are very important when picking up potential Alzheimer's, because elderly individuals themselves may not be aware that their function is declining. Therefore, if you have concerns, I would definitely encourage your grandmother to get in to see her primary care doctor
as soon as possible.
Her doctor will be able to perform an assessment of your grandmother's cognitive function, an important first step in evaluating for Alzheimer's. They will also be able to assess for any other potential medical issues, such as vitamin deficiency or a thyroid problem, which may also cause trouble with cognitive function and are easily treated. If it turns out your grandmother does have Alzheimer's her doctor will be able to make recommendations about how to treat it.